placement_rule: supports show origin placement rules

[HuSharp]

What problem does this PR solve?

Issue Number: close #46617

Problem Summary:

mysql> use test;
mysql> CREATE PLACEMENT POLICY follower3 FOLLOWERS=3;
mysql> CREATE PLACEMENT POLICY follower5 FOLLOWERS=5;

mysql> CREATE TABLE t1 (
  country VARCHAR(10) NOT NULL,
  userdata VARCHAR(100) NOT NULL
) PLACEMENT POLICY=follower3 PARTITION BY LIST COLUMNS (country) (
PARTITION A VALUES IN ('DE', 'FR', 'GB') PLACEMENT POLICY=follower5,
PARTITION B VALUES IN ('M')
);

mysql> SHOW PLACEMENT format = raw\G;
*************************** 1. row ***************************
          Target: POLICY follower3
       Placement: FOLLOWERS=3
Scheduling_State: NULL
*************************** 2. row ***************************
          Target: POLICY follower5
       Placement: FOLLOWERS=5
Scheduling_State: NULL
*************************** 3. row ***************************
          Target: Rule pd
       Placement:
{
    "group_id": "pd",
    "group_index": 0,
    "group_override": false,
    "rules": [
        {
            "group_id": "pd",
            "id": "default",
            "start_key": "",
            "end_key": "",
            "role": "voter",
            "count": 3
        }
    ]
}

Scheduling_State: NULL
*************************** 4. row ***************************
          Target: Rule TiDB_DDL_104
       Placement:
{
    "group_id": "TiDB_DDL_104",
    "group_index": 40,
    "group_override": true,
    "rules": [
        {
            "group_id": "TiDB_DDL_104",
            "id": "table_rule_104_0",
            "index": 40,
            "start_key": "7480000000000000ff6800000000000000f8",
            "end_key": "7480000000000000ff6900000000000000f8",
            "role": "voter",
            "count": 4,
            "label_constraints": [
                {
                    "key": "engine",
                    "op": "notIn",
                    "values": [
                        "tiflash"
                    ]
                }
            ]
        },
        {
            "group_id": "TiDB_DDL_104",
            "id": "partition_rule_105_0",
            "index": 80,
            "start_key": "7480000000000000ff6900000000000000f8",
            "end_key": "7480000000000000ff6a00000000000000f8",
            "role": "voter",
            "count": 4,
            "label_constraints": [
                {
                    "key": "engine",
                    "op": "notIn",
                    "values": [
                        "tiflash"
                    ]
                }
            ]
        },
        {
            "group_id": "TiDB_DDL_104",
            "id": "partition_rule_106_0",
            "index": 80,
            "start_key": "7480000000000000ff6a00000000000000f8",
            "end_key": "7480000000000000ff6b00000000000000f8",
            "role": "voter",
            "count": 4,
            "label_constraints": [
                {
                    "key": "engine",
                    "op": "notIn",
                    "values": [
                        "tiflash"
                    ]
                }
            ]
        }
    ]
}

Scheduling_State: NULL
*************************** 5. row ***************************
          Target: Rule TiDB_DDL_105
       Placement:
{
    "group_id": "TiDB_DDL_105",
    "group_index": 80,
    "group_override": true,
    "rules": [
        {
            "group_id": "TiDB_DDL_105",
            "id": "partition_rule_105_0",
            "index": 40,
            "start_key": "7480000000000000ff6900000000000000f8",
            "end_key": "7480000000000000ff6a00000000000000f8",
            "role": "voter",
            "count": 6,
            "label_constraints": [
                {
                    "key": "engine",
                    "op": "notIn",
                    "values": [
                        "tiflash"
                    ]
                }
            ]
        }
    ]
}

Scheduling_State: NULL
*************************** 6. row ***************************
          Target: Rule tiflash
       Placement:
{
    "group_id": "tiflash",
    "group_index": 120,
    "group_override": false,
    "rules": null
}

Scheduling_State: NULL
6 rows in set (0.00 sec)

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[tiprow]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[ti-chi-bot]

PR needs rebase.

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[nolouch]

@HuSharp plz resolve conflicts and make it reviewable.

[codecov]

Codecov Report

Attention: Patch coverage is 2.94118% with 66 lines in your changes missing coverage. Please review.

Project coverage is 71.6826%. Comparing base (ce9e9ef) to head (cebac63).
Report is 2447 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #46750        +/-   ##
================================================
+ Coverage   71.0497%   71.6826%   +0.6328%     
================================================
  Files          1368       1414        +46     
  Lines        401707     416758     +15051     
================================================
+ Hits         285412     298743     +13331     
- Misses        96439      99168      +2729     
+ Partials      19856      18847      -1009     

Flag	Coverage Δ
integration	43.6283% <2.9411%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9663% <ø> (ø)
parser	∅ <ø> (∅)
br	47.8567% <ø> (-5.0368%)	⬇️

[nolouch]

overall lgtm. plz add some tests

[nolouch]

/retest-required

[ti-chi-bot]

[FORMAT CHECKER NOTIFICATION]

Notice: To remove the do-not-merge/needs-tests-checked label, please finished the tests then check the finished items in description.

For example:

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

_{📖 For more info, you can check the "Contribute Code" section in the development guide.}

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: nolouch
Once this PR has been reviewed and has the lgtm label, please assign bornchanger, d3hunter, tangenta, yudongusa for approval. For more information see the Kubernetes Code Review Process.

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-12-27 07:52:48.708768002 +0000 UTC m=+1638659.745994926: ☑️ agreed by nolouch.

[nolouch]

/retest-required t

[ti-chi-bot]

@HuSharp: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/build	cebac63	link	true	/test build
pull-mysql-client-test	cebac63	link	true	/test pull-mysql-client-test
idc-jenkins-ci-tidb/check_dev	cebac63	link	true	/test check-dev
idc-jenkins-ci-tidb/check_dev_2	cebac63	link	true	/test check-dev2
idc-jenkins-ci-tidb/mysql-test	cebac63	link	true	/test mysql-test
idc-jenkins-ci-tidb/unit-test	cebac63	link	true	/test unit-test
pull-integration-ddl-test	cebac63	link	true	/test pull-integration-ddl-test
pull-br-integration-test	cebac63	link	true	/test pull-br-integration-test
pull-lightning-integration-test	cebac63	link	true	/test pull-lightning-integration-test
pull-unit-test-ddlv1	cebac63	link	true	/test pull-unit-test-ddlv1

Full PR test history. Your PR dashboard.

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