server: fix decode issue for prefetch point plan index keys (#50037)

[ti-chi-bot]

This is an automated cherry-pick of #50037

What problem does this PR solve?

Issue Number: close #50012

Problem Summary:

The second parameter of tablecodec.DecodeHandleInUniqueIndexValue indicates whether index KVs belong to a clustered-index table. Previously, it was always false, causing decoding error and panic.

What changed and how does it work?

• Set the parameter properly.
• In order to pass the check like BatchGet req does not set the resource tag, tid: 123, stack: goroutine 20153 [running], I also set the resource group tagger by the digest of all SQLs.
• Add an integration test.

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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@cd073ea). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, qw4990

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• OWNERS [hawkingrei,qw4990]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-23 13:41:53.200090755 +0000 UTC m=+881754.764388460: ☑️ agreed by qw4990.
• 2024-01-23 13:49:01.63584607 +0000 UTC m=+882183.200143775: ☑️ agreed by hawkingrei.