feat: separate mariadb driver

[SychO9]

Fixes #0000

Changes proposed in this pull request:

• Fixes checking of MariaDB in the migrations to using ->isMaria()
• Adds mariadb as a separate database driver, laravel 11 has done the same in order to more easily handle the growing differences between mysql and mariadb.
• This will not break things for instances using mariadb under the mysql driver. But we need to document switching to mariadb driver nonetheless.

Screenshot

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

Required changes:

• Related documentation PR: (Remove if irrelevant)

[luceos]

@SychO9 feel free to merge. I will do a test run early this week on Nightly (if it doesn't already auto fix with this).