statistics: separte complex file and forbid embedding

[Yisaer]

Signed-off-by: yisaer disxiaofei@163.com

What problem does this PR solve?

Issue Number: close #36284

Problem Summary:

What is changed and how it works?

Move index and Column into different file from histogram.go, avoid embedding CMSketch and TopN in order to help us to check nil.

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]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• hawkingrei
• xuyifangreeneyes

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[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/8dbaa509e72f9fde302da6c6a89d92fe25fa6687

[hawkingrei]

If Histogram forbid embedding, It will be better.

[Yisaer]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 6112214

[Yisaer]

/run-unit-test

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	✅ all 11 tests passed	39 min	Fixed
idc-jenkins-ci/integration-cdc-test	🟢 all 36 tests passed	27 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	12 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	8 min 23 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 56 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 24 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	4 min 33 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 14 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 5 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed