gc: Fix GcKeys task doesn't work when called with multiple keys (#11248)

[ti-srebot]

cherry-pick #11248 to release-5.0
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# In tikv repo:
git pr https://github.com/tikv/tikv/pull/11283

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git push git@github.com:ti-srebot/tikv.git pr/11283:release-5.0-68c7ecb41c8d

---

What problem does this PR solve?

Issue Number: close #11217

Problem Summary:

The problem is because gc_worker passes the range with z-prefixed keys to get regions in the range, whereas RegionInfoProvider actually accepts keys without z-prefixed. So it causes get_regions_in_range returns incorrect results leading to unexpected behavior of handling GcKeys task.

Apart from that, find two more bugs:

• the implementation of gc_keys wrongly assume the start key and end key of region are z-prefixed
• handle_get_regions_in_range doesn't returned all covered regions of the keys.

What is changed and how it works?

Proposal: xxx

What's Changed:

• Add a wrapper RangeKey to remove confusing z-prefixed keys in RegionInfoProvider
• Fix the the implementation of gc_keys
• Fix handle_get_regions_in_range logic
• Add a metrics to show how many mvcc deletion version is handled
  

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Manual test: using an update heavy workload, and do select to trigger scan, the key_skipped_count(due to too many mvcc deleted versions left) is greatly reduced.

Before

After

Release note

Fix mvcc deletion may not be dropped by compaction filter GC 

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• hicqu
• yiwu-arbug

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[ti-srebot]

/run-all-tests

[ti-srebot]

@Connor1996 you're already a collaborator in bot's repo.

[MyonKeminta]

@yiwu-arbug The conflicts are not resolved yet in this PR, and the other PR for 5.1 branch.

[Connor1996]

/merge

[ti-chi-bot]

@Connor1996: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 6061b5d

[Connor1996]

/test