log_backup: fix panic during advancer owner transfer (#52671)

[ti-chi-bot]

This is an automated cherry-pick of #52671

What problem does this PR solve?

Issue Number: close #52597

Problem Summary:

1. When losing the advancer ownership, the channel for subscription may be full.
2. the consumer has already gone due to the canceled context. Hence making the producer(subscription) goroutine stuck.
3. After the graceful shutdown period, the output channel will be eventually closed and we will get a send on closed channel panic.

What changed and how does it work?

• When sending to the channel, also select the context.
• Catch all panic and convert them to errors (so we can retry.)

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.

Fixed a bug where TiDB may panic when log backup enabled and PD is unreachable.

[YuJuncen]

/retest-required

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3pointer, YuJuncen

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Needs approval from an approver in each of these files:

• OWNERS [3pointer,YuJuncen]
• br/OWNERS [3pointer,YuJuncen]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-23 09:29:18.152969881 +0000 UTC m=+2336711.910105454: ☑️ agreed by YuJuncen.
• 2024-05-23 09:35:20.345633734 +0000 UTC m=+2337074.102769307: ☑️ agreed by 3pointer.

[BornChanger]

/retest

[codecov]

Codecov Report

Attention: Patch coverage is 95.55556% with 2 lines in your changes are missing coverage. Please review.

Please upload report for BASE (release-7.5@1e19051). Learn more about missing BASE report.

Additional details and impacted files

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##             release-7.5     #53060   +/-   ##
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Flag	Coverage Δ
unit	71.9994% <95.5555%> (?)

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Components	Coverage Δ
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parser	∅ <0.0000%> (?)
br	53.4688% <0.0000%> (?)