PageStorage: Fix pages are not deleted under some cases (#5069)

[ti-chi-bot]

This is an automated cherry-pick of #5069

What problem does this PR solve?

Issue Number: close #5054

Problem Summary: as the issue described

What is changed and how it works?

• StoragePool only need to remove DTFiles ids that are not exist in the V3.data, cause we perform force transform from V2.data to V3.data when restore
• Keep tombstone when merging the delta version for page entries in V2

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

• Manual test steps:
  • Deploy cluster and load some data into TiFlash with storage.format_version = 3
  • Change the storage.format_version = 4
  • Use alter table t compact tiflash replica to perform delta-merge
  • Check that the old DTFiles are removed

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

None

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[JaySon-Huang]

The changes are already merged by #5070