Cherry pick 52834 to release 8.1

[YuJuncen]

What problem does this PR solve?

Issue Number: close #52791, close #52792

Problem Summary:
When dropping a subscription manager, the pending events will be dropped. So the test case will fail.

What changed and how does it work?

Wait until it seems there isn't new events.

Check List

Tests

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

> go test --count=100 -run '^TestSomeOfStoreUnsupported|TestStoreRemoved$' github.com/pingcap/tidb/br/pkg/streamhelper
ok      github.com/pingcap/tidb/br/pkg/streamhelper     40.463s

• 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 @YuJuncen. Thanks for your PR.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from yujuncen and additionally assign bb7133, benjamin2037, benmeadowcroft, d3hunter, winoros, zanmato1984 for approval(Please ensuring that each of them provides their approval before proceeding). For more information see the Code Review Process.

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Needs approval from an approver in each of these files:

• OWNERS
• br/OWNERS
• br/pkg/storage/OWNERS
• dumpling/OWNERS
• lightning/OWNERS
• pkg/autoid_service/OWNERS
• pkg/bindinfo/OWNERS
• pkg/config/OWNERS
• pkg/ddl/OWNERS
• pkg/distsql/OWNERS
• pkg/disttask/OWNERS
• pkg/domain/OWNERS
• pkg/executor/importer/OWNERS
• pkg/expression/OWNERS
• pkg/infoschema/OWNERS
• pkg/lightning/OWNERS
• pkg/meta/OWNERS
• pkg/owner/OWNERS
• pkg/parser/OWNERS
• pkg/planner/OWNERS
• pkg/session/OWNERS
• pkg/sessionctx/variable/OWNERS
• pkg/statistics/OWNERS
• pkg/table/OWNERS
• pkg/tablecodec/OWNERS

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[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

1. It must be approved by the approvers firstly.
2. AFTER it has been approved by approvers, please wait for the cherry-pick merging approval from triage owners.

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[ti-chi-bot]

[FORMAT CHECKER NOTIFICATION]

Notice: To remove the do-not-merge/invalid-title label, please follow title format, for example pkg [, pkg2, pkg3]: what is changed or *: what is changed.

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[YuJuncen]

(It is empty now...)

[ti-chi-bot]

@YuJuncen: 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
pull-integration-ddl-test	618f61e	link	true	/test pull-integration-ddl-test
pull-lightning-integration-test	618f61e	link	true	/test pull-lightning-integration-test
pull-mysql-client-test	618f61e	link	true	/test pull-mysql-client-test
pull-br-integration-test	618f61e	link	true	/test pull-br-integration-test
pull-unit-test-ddlv1	618f61e	link	true	/test pull-unit-test-ddlv1
idc-jenkins-ci-tidb/build	618f61e	link	true	/test build
idc-jenkins-ci-tidb/check_dev	618f61e	link	true	/test check-dev
idc-jenkins-ci-tidb/check_dev_2	618f61e	link	true	/test check-dev2
idc-jenkins-ci-tidb/unit-test	618f61e	link	true	/test unit-test
idc-jenkins-ci-tidb/mysql-test	618f61e	link	true	/test mysql-test

Full PR test history. Your PR dashboard.

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