Add MariaDB to our CI matrix

[GuySartorelli]

MariaDB is essentially a plug-and-play equivalent to MySQL, but it does have some differences and we aren’t currently regression testing against it.

We decided in a recent retrospective that we should add MariaDB to our CI matrix.

We can do so my moving the MySQL 5.7 builds to be only on prefer lowest, and replace the old 5.7 build with MariaDB.

Acceptance criteria

• All our CMS 5 builds are running a MariaDB build.

Exclude

• Any build failures will be handled in a follow up card.

PR

• https://github.com/silverstripe/gha-generate-matrix/pull/71
• https://github.com/silverstripe/gha-ci/pull/92
• https://github.com/silverstripe/gha-generate-matrix/pull/73
• https://github.com/silverstripe/gha-ci/pull/93

Tests

CMS 5

• https://github.com/sabina-talipova/recipe-kitchen-sink/actions/runs/6765065012/job/18385882920

  CMS 4

• https://github.com/sabina-talipova/recipe-kitchen-sink/actions/runs/6765931440

[GuySartorelli]

PRs merged