mariadb: add mariadb-base-image to facilitate upstream "nightlies"

[grooverdan]

Q	A
Type	improvement
Fixed issues

Summary

From #6426, add a 90 second test to ensure Doctrine DBAL remains compatible with MariaDB, and users aren't the ones to discover incompatibilities (like #6361).

A quay.io/mariadb-foundation/mariadb-devel:verylatest is what is going to be in the next MariaDB release, including unintentionally breaking features, this is a good change to let MariaDB know before they have committed via release to the stability of the change.

Alternates:

• Let user's find incompatibilities
• Replace last few matrix includes with mariadb-base-image: "quay.io/mariadb-foundation/mariadb-devel" tests
• Let MariaDB upstream run DBAL tests if they want to (please don't, I'm struggling to maintain the few language tests that we do run).

[greg0ire]

Since this isn't going to break with new commits on this repo, I'd rather this be a scheduled run.

[grooverdan]

6435 instead.