As MariaDB 10.5 has been removed from Debian Sid and MariaDB 10.6 has
entered it, the Salsa-CI testing needs to adapt.

To achieve this, essentially sync most the the salsa-ci.yml contents from
https://salsa.debian.org/mariadb-team/mariadb-server/-/tree/debian/latest

This includes removing Stretch builds, as Stretch does not support uring
nor pmem libraries, which MariaDB 10.6 depends on.

Also add a couple Lintian overrides to make Salsa-CI pass.

NOTE TO MERGERS: This commit is made on 10.6 branch and can be merged to
all later branches (10.7, 10.8, 10.9..) for now, but later somebody needs
to go in and update all the testing stages to do the upgrade testing
correctly for 10.6->10.7->10.8->10.9 etc.