gc_worker: Skip TiFlash nodes when doing UnsafeDestroyRange and Green GC (#15505)

[sre-bot]

cherry-pick #15505 to release-3.1

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What problem does this PR solve?

Issue Number: close #15496

Problem Summary: GC delete range phase and (if green gc is enabled) resolve lock phase cannot successfully run when there are TiFlash nodes in the cluster.

What is changed and how it works?

What's Changed: Filters out TiFlash nodes when sending UnsafeDestroyRange and Green GC related stuff, according to the store's "engine" label. But note that it's possible to be broken when the label is incorrectly configured (see tikv/tikv#7153).

How it Works: For a TiFlash node, it uses other approach to delete dropped tables, so it's safe to skip sending UnsafeDestroyRange requests; it has only learner peers and their data must exist in TiKV, so it's safe to skip physical resolve locks for it. So in theory GC is still correct.

Related changes

• Need to cherry-pick to the release branch
  • release-3.1 (which supports TiFlash)

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  • Need to be test if it actually works in a TiFlash-equipped cluster. (Help wanted)

Side effects

Release note

(I'm not sure if this is needed since it's related to TiFlash)

• Fixes the issue that GC may not work in a cluster that has TiFlash

[sre-bot]

/run-all-tests