Replaced deprecated MySQL aliases for MariaDB tests (#1200)

This fixes the recently failing GitHub Actions test workflows, in which
the MariaDB Docker container failed to start.

The issue seems to have been using the `mysqladmin` command for health
checking in `test.yml`, probably due to the following change in
MariaDB v11.0.1:
(Copied from https://mariadb.com/kb/en/mariadb-11-0-1-release-notes/)
"""
## Docker Official Images
* 11.0, unlike previous version, no longer includes mysql named
  compatible executable symlinks inside the container.
"""
https://mariadb.com/kb/en/mysqladmin/ mentions that `mariadb-admin` is
now the new name of the script (previously `mysqladmin`).

Also replaced the `MYSQL_DATABASE` and `MYSQL_ROOT_PASSWORD` environment
variables with their new names (based on the docs:
https://mariadb.com/kb/en/mariadb-server-docker-official-image-environment-variables/).

.github/workflows/test.yml

@@ -63,11 +63,11 @@ jobs:
       mariadb:
         image: mariadb:latest
         env:
-          MYSQL_DATABASE: mariadb
-          MYSQL_ROOT_PASSWORD: mariadb
+          MARIADB_DATABASE: mariadb
+          MARIADB_ROOT_PASSWORD: mariadb
         ports:
           - 3307:3306
-        options: --health-cmd="mysqladmin ping" --health-interval=10s --health-timeout=5s --health-retries=3
+        options: --health-cmd="mariadb-admin ping" --health-interval=10s --health-timeout=5s --health-retries=3
 
     steps:
       - uses: actions/checkout@v3