executor: Fix losing the auth string on changing SSL/TLS requirements (#25268)

[ti-srebot]

cherry-pick #25268 to release-5.1
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/25349

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

git push [email protected]:ti-srebot/tidb.git pr/25349:release-5.1-faf139eae1f1

---

What problem does this PR solve?

Issue Number: close #25225

Problem Summary: An ALTER USER ... REQUIRE SSL would cause the authentication string of the user to get overwritten with an empty string

What is changed and how it works?

How it Works:

• Don't change the authentication_string unless we have an AuthOpt
• Check for SUPER when changing other accounts auth options.

Check List

Tests

• Unit test (more might be useful, but there is one already)

Release note

• Important security issue for handling ALTER USER statements

[ti-srebot]

/run-all-tests

[ti-srebot]

@dveeden please accept the invitation then you can push to the cherry-pick pull requests.
https://github.com/ti-srebot/tidb/invitations

[zhouqiang-cl]

/merge

[ti-chi-bot]

@zhouqiang-cl: /merge in this pull request requires 2 approval(s).

In response to this:

/merge

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• morgo
• tiancaiamao

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[zhouqiang-cl]

/merge

[ti-chi-bot]

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

Commit hash: 3484640

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.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

[time-and-fate]

/run-check_dev