Deb: Sync Salsa-CI from Debian MariaDB 10.5 repository

Since Debian Sid now has MariaDB 10.6, we can't do any upgrade tests in
Debian Sid for the 10.5 branch anymore. It would just fail with downgrade
errors.

Also, since MariaDB 10.5 is no longer in Sid, we can't even test 10.5.x
to 10.5.y upgrades in Sid.

Instead the 10.5 branch salsa-ci.yml should run all builds and tests based
on Debian Bullseye, which has MariaDB 10.5 (only).

To achieve this, essentially sync most the the salsa-ci.yml contents from
https://salsa.debian.org/mariadb-team/mariadb-10.5/-/tree/bullseye

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

NOTE TO MERGERS: This commit is intended for the 10.5 branch only, do not
merge anything from it on 10.6 or any other branch.

debian/source/lintian-overrides

@@ -23,8 +23,10 @@ version-substvar-for-external-package libmariadbd-dev -> libmariadbclient-dev
 # ColumnStore not used in Debian, safe to ignore. Reported upstream in https://jira.mariadb.org/browse/MDEV-24124
 source-is-missing storage/columnstore/columnstore/utils/jemalloc/libjemalloc.so.2
 # Must be fixed upstream
-source-is-missing storage/mroonga/vendor/groonga/examples/dictionary/html/js/jquery-ui-1.8.18.custom.js line 58 is 273 characters long (>256)
+source-is-missing storage/mroonga/vendor/groonga/examples/dictionary/html/js/jquery-ui-1.8.18.custom.js *
 # Intentional control relationships
 version-substvar-for-external-package Replaces (line 216) ${source:Version} libmariadbd-dev -> libmariadbclient-dev
 version-substvar-for-external-package Replaces (line 66) ${source:Version} libmariadb-dev -> libmysqlclient-dev
 version-substvar-for-external-package Replaces (line 66) ${source:Version} libmariadb-dev -> libmysqld-dev
+# We can't change build dependencies on a stable branch (10.5..10.8) so just override this
+missing-build-dependency-for-dh-addon systemd *