br/stream: implement segmented restore

[YuJuncen]

What problem does this PR solve?

Issue Number: close #(TBD)

Problem Summary:

From __agent_doc/main.md

You need to implement a feature -- segmented restore.

Now, br restore point requires the user to finish restore to a point-in-time within oneshot.

We want br restore point can be "segmented", like:

br restore point --pd 127.0.0.1:2379 -s local:///Volumes/eXternal/Cache/tmp/20260122_003925/incr --restored-ts 463736294698909699 --full-backup-storage local:///Volumes/eXternal/Cache/tmp/20260122_003925/full --last=false
/br restore point --pd 127.0.0.1:2379 -s local:///Volumes/eXternal/Cache/tmp/20260122_003925/incr --restored-ts 463736295708426243 --start-ts 463736294698909699 --last=false
/br restore point --pd 127.0.0.1:2379 -s local:///Volumes/eXternal/Cache/tmp/20260122_003925/incr --restored-ts ... --start-ts 463736295708426243 --last=true

But for now, it is impossible. There are something we have known: tiflash replicas may be added back too early, indices may not be properly recreated... But more are unknown unknown.

---

What changed and how does it work?

• Persisted {TiFlash|Ingest} recorder status during segemented restore.
• Use dedicated function to load id maps from previous restore.
• Added a real-tikv-test case to verify the function.

Check List

Tests

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

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[ti-chi-bot]

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[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
idc-jenkins-ci-tidb/check_dev_2	dea4ab0	link	true	/test check-dev2
pull-integration-realcluster-test-next-gen	dea4ab0	link	true	/test pull-integration-realcluster-test-next-gen
idc-jenkins-ci-tidb/check_dev	dea4ab0	link	true	/test check-dev
pull-br-integration-test	dea4ab0	link	true	/test pull-br-integration-test
pull-build-next-gen	dea4ab0	link	true	/test pull-build-next-gen
pull-mysql-client-test	dea4ab0	link	true	/test pull-mysql-client-test
idc-jenkins-ci-tidb/build	dea4ab0	link	true	/test build
pull-mysql-client-test-next-gen	dea4ab0	link	true	/test pull-mysql-client-test-next-gen
idc-jenkins-ci-tidb/mysql-test	dea4ab0	link	true	/test mysql-test
pull-integration-e2e-test	dea4ab0	link	true	/test pull-integration-e2e-test
pull-unit-test-next-gen	dea4ab0	link	true	/test pull-unit-test-next-gen
idc-jenkins-ci-tidb/unit-test	dea4ab0	link	true	/test unit-test

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