lightning: Add source dir existence check for s3 (#30674)

[ti-srebot]

cherry-pick #30674 to release-5.2
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/30713

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/30713:release-5.2-4b48e55ae9c7

---

What problem does this PR solve?

Issue Number: close #28031, close #30709

Problem Summary:

What is changed and how it works?

• Add a WalkDir after build remote storage to check whether target directory contains at least one regular file.
• Remove the deprecated skip-check-path parameter for br and lightning because the requirement privilege is too high.

Check List

Tests

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

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

Fix the but that lightning doesn't report error if s3 storage path not exist.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• glorv
• gozssky

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[sleepymole]

/merge

[ti-chi-bot]

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

Commit hash: 3856bbc

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/0b7d465aa5b00baeb624f19dc9faeb7e64476b32