FR: skip EOL checks in mariadb_repo_setup

The mariadb_repo_setup script refuses to install if the detected operating system version, or the requested MariaDB server major version, is beyond its EOL life and so no longer supported.

This is a good idea in general, but for testing purposes it may at times still be required to set up such older versions.

As we still provide the actual version specific repositories for these older versions I suggest to add options --skip-eol-check and --skip-os-eol-check options that allow to disable these checks explicitly when really needed.