br: restore checksum shouldn't rely on backup checksum (#56712)

[ti-chi-bot]

This is an automated cherry-pick of #56712

What problem does this PR solve?

Issue Number: close #56373

Problem Summary:

What changed and how does it work?

1. Disable checksum by default only for snapshot backup process.
2. Keep checksum enabled for the rest
3. During snapshot restore, verify admin checksum by doing xor on all meta file checksums, so it doesn't rely on backup generating the CRC for the database.

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.

The default behavior of doing checksum during full backup has changed from enabled to disabled. 
The meaning of checksum flag is kind of ambiguous here, it doesn't mean we don't do the checksum of files when doing backup, instead we don't do checksum to compare from coprocessor side to the br side to improve the performance

[ti-chi-bot]

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Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/check_dev_2	ac7f0e9	link	true	/test check-dev2
idc-jenkins-ci-tidb/unit-test	ac7f0e9	link	true	/test unit-test
idc-jenkins-ci-tidb/check_dev	ac7f0e9	link	true	/test check-dev
idc-jenkins-ci-tidb/mysql-test	ac7f0e9	link	true	/test mysql-test
idc-jenkins-ci-tidb/build	ac7f0e9	link	true	/test build

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