Test tool and unit test improvements for 6.5

[jorbin]

Previously:

• #58955 (6.4)
• #57841 (6.3)
• #56793 (6.2)
• #55652 (6.1)
• #54725 (6.0)
• #53363 (5.9)
• #52625 (5.8)
• #51802 (5.7)
• #51344 (5.6)

This ticket is for various fixes and improvements in PHPUnit tests that don't have a more specific ticket, as well as general improvements to the GitHub Actions workflows that run automated testing.

[jorbin]

Facepalm #59647

This updates the unit test matrix strategy for MariaDB to include the latest short-term stable release, 11.2. Though 11.0 and 11.1 are still maintained (until June and August of 2024 respectively), testing only against the most recent short-term release should suffice until a broader discussion can be had around support for short-term or innovation releases in database software for the project.

Trac ticket: https://core.trac.wordpress.org/ticket/59806

[desrosj]

In 57152:

Build/Test Tools: Update the MariaDB test strategy matrix.

This updates the test strategy matrix in the PHPUnit test GitHub Actions workflow to include the most recent MariaDB release, 11.2.

While 11.0 and 11.1 are still maintained, all three are short-term stable releases, which see support dropped after 1 year.

Until a larger discussion around how the project supports database software releases with shorter support windows takes place (short-term in MariaDB or “innovation” releases in MySQL), testing only against the latest short-term release should be sufficient.

Props johnbillion, l1nuxjedi.
See #59806.

Merged in https://core.trac.wordpress.org/changeset/57152.