server: fix authentication with MySQL 5.1 and older clients (#29732)

[bb7133]

cherry-pick #29732 to release-5.3

---

What problem does this PR solve?

Issue Number: close #29725

Problem Summary:

handleAuthPlugin checks for the ClientPluginAuth capability but this didn't set the AuthPlugin causing readOptionalSSLRequestAndHandshakeResponse to return an error.

Note that this allows authentication for users that use mysql_native_password to work, but users using caching_sha2_passwords won't work.

This does now return a more specific error in case authentication with caching_sha2_password is used.

[dvaneeden@dve-carbon ~]$ ~/opt/mysql/5.1.73/bin/mysql -h 127.0.0.1 -u sha -P 4000 -psha
ERROR 1105 (HY000): ERROR 1251 (08004): Client does not support authentication protocol requested by server; consider upgrading MySQL client

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Verify the connection with MySQL client v5.1:

sh> mysql -u root -h 127.0.0.1 -P 4000

• 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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• djshow832
• wjhuang2016

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[sre-bot]

Please follow PR Title Format:

• pkg [, pkg2, pkg3]: what is changed

Or if the count of mainly changed packages are more than 3, use

• *: what is changed

After you have format title, you can leave a comment /run-check_title to recheck it

[bb7133]

/run-check_title

[bb7133]

/merge

[ti-chi-bot]

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

Commit hash: 2eeac32

[bb7133]

/run-check_dev

[bb7133]

/merge

[zhouqiang-cl]

/run-check_dev

[bb7133]

/merge

[ti-chi-bot]

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

Commit hash: 28e6d8d

[ti-chi-bot]

@bb7133: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[bb7133]

/run-check_dev

[bb7133]

/run-check_dev