log-backup: remove the checkpoint after removal

[YuJuncen]

Signed-off-by: Yu Juncen yujuncen@pingcap.com

What problem does this PR solve?

Issue Number: close #36423

Problem Summary:
When we removed the task, we won't remove the global checkpoint and the metric, which is misleading.

What is changed and how it works?

Remove the global checkpoint and the metric when we have watched the task removed.
NOTE: for now, all TiDB instances would listen to the task keys, we may do unnecessary works.

Check List

Tests

• Unit test (TBD)

Release note

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

Fixed a bug that may cause the information of the checkpoint being stale.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• 3pointer
• Leavrth

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/9c334568cb9f6c0d878b86705f910edde3bcaf8c

[3pointer]

LGTM

[YuJuncen]

/merge

[ti-chi-bot]

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

Commit hash: 32163d1

[ti-srebot]

cherry pick to release-6.2 in PR #36508

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! New failing [1] after this pr merged.
These new failed integration tests seem to be caused by the current PR, please try to fix these new failed integration tests, thanks!

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-ddl-test	🟥 failed 2, success 4, total 6	13 min	New failing
idc-jenkins-ci-tidb/integration-common-test	🟢 all 11 tests passed	46 min	Existing passed
idc-jenkins-ci/integration-cdc-test	🟢 all 36 tests passed	27 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	18 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 12 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 0 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	4 min 42 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 32 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	2 min 52 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed