Fix background gc when rows covered by delete range is larger than stable (#3657)

[ti-chi-bot]

This is an automated cherry-pick of #3657

What problem does this PR solve?

Issue Number: close #3659

Problem Summary: If some segments was generated by logical split, the new segments will keep the delete range of the old segment. And by the old gc logic, the rows in stable covered by delete range is larger than the valid rows in the stable which will skip gc on these segments.
The original purpose of this check is to prevent small segments to merge delta. But after some detail investigation, this check is really unnecessary.

What is changed and how it works?

1. remove the check to forbid gc when stable is smaller than delta
2. use the new log macro

Check List

Tests

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

1. deploy a cluster with master version and load tpcc data
2. set replica to 0 and watch the change in tiflash storage space
3. patch to this fixed version and watch the change in tiflash storage space

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• flowbehappy

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[lidezhu]

/run-all-tests

[lidezhu]

/merge

[ti-chi-bot]

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[ti-chi-bot]

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

Commit hash: 54228cf