MDEV-35018 MDL BF-BF conflict on DROP TABLE

[sciascid]

• [x] The Jira issue number for this PR is: MDEV-35018

Description

The patch fixes a case where two Galera appliers would conflict at MDL level, while applying "DROP TABLE child" and "UPDATE parent". Where "child" has a foreign key to table "parent". DROP TABLE takes MDL locks on both child and its parent table, however insufficient galera certifications keys were appended, which caused these two operation to apply concurrently.

Release Notes

Nothing.

How can this PR be tested?

The patch comes with MTR tests.

Basing the PR against the correct MariaDB version

• [ ] This is a new feature or a refactoring, and the PR is based against the main branch.
• [x] This is a bug fix, and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• [x] I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• [x] For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.

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[sysprg]

Thanks, the fix has been merged with the head revision: https://github.com/MariaDB/server/commit/841a7d391bead2e486967ed73aed091ac633b4f2 Additional changes: https://github.com/MariaDB/server/commit/50cf189717a3fce90a9f2407ed57e59c108f91ef (to overcome MDEV-26266 regression)