localbackend: release the service safe point on finish checksum

[D3Hunter]

What problem does this PR solve?

Issue Number: ref #61702, close #62142

Problem Summary:

What changed and how does it work?

send a request with TTL=0 to remove it, see https://github.com/tikv/pd/blob/29ead019cd0982a3120bc79d4a4d19199dab2279/server/grpc_service.go#L2280-L2284 too

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

with master, we can see the service safe point still exist after lightning exist, it will expire after 10m

➜  lightning /Users/user/code/pingcap/tidb/bin/tidb-lightning-master --config test.toml
Verbose debug logs will be written to lightning.log

tidb lightning exit successfully
➜  lightning etcdctl --endpoints localhost:2379 get --prefix ""|grep -a lightning
/pd/7522392937985088901/gc/safe_point/service/lightning-c8a20fff-07bd-4744-bfa5-a12e529847c5
{"service_id":"lightning-c8a20fff-07bd-4744-bfa5-a12e529847c5","expired_at":1751444458,"safe_point":459130498717057084}

with this PR, it's removed after exist

➜  lightning /Users/user/code/pingcap/tidb/bin/tidb-lightning -V
Release Version: v9.0.0-beta.2.pre-22-ga116ca4c78
Git Commit Hash: a116ca4c789a3c751fdee29bebada13594668312
Git Branch: imp-checksum-task-ks
Go Version: go1.23.10
UTC Build Time: 2025-07-02 08:16:00
Race Enabled: false
➜  lightning /Users/user/code/pingcap/tidb/bin/tidb-lightning --config test.toml
Verbose debug logs will be written to lightning.log

tidb lightning exit successfully
➜  lightning etcdctl --endpoints localhost:2379 get --prefix ""|grep -a lightning

• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

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

None

[tiprow]

Hi @D3Hunter. Thanks for your PR.

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[codecov]

Codecov Report

Attention: Patch coverage is 87.09677% with 4 lines in your changes missing coverage. Please review.

Project coverage is 73.5495%. Comparing base (94bfb3d) to head (2e7e178).
Report is 18 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #62143        +/-   ##
================================================
+ Coverage   72.9233%   73.5495%   +0.6262%     
================================================
  Files          1739       1770        +31     
  Lines        482858     493886     +11028     
================================================
+ Hits         352116     363251     +11135     
+ Misses       109170     108349       -821     
- Partials      21572      22286       +714     

Flag	Coverage Δ
integration	45.2002% <87.0967%> (?)
unit	72.2595% <80.0000%> (+0.0806%)	⬆️

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

Components	Coverage Δ
dumpling	52.7804% <ø> (ø)
parser	∅ <ø> (∅)
br	45.6537% <ø> (-0.6771%)	⬇️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: GMHDBJD, lance6716

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Details

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• lightning/OWNERS [GMHDBJD]
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-07-02 09:02:31.063420176 +0000 UTC m=+1472003.786599158: ☑️ agreed by GMHDBJD.
• 2025-07-02 09:22:47.855020481 +0000 UTC m=+1473220.578199463: ☑️ agreed by lance6716.

[D3Hunter]

/retest

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In response to this:

/retest

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[D3Hunter]

/retest

[tiprow]

@D3Hunter: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

Details

In response to this:

/retest

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