Salsa-CI: Copy most of Salsa-CI from Debian 10.5

- Use new Salsa-CI templates just like downstream does
- Also apply adaptations needed for native MariaDB to
  build correctly on Salsa-CI
- Adapt for mysql-8.0 now in Debian Sid, keep also mysql-5.7 test
- Test TLSv1.3 to ensure it does not regress
- Remove Snappy compression from autopkgtest as it not longer works

debian/tests/smoke

@@ -68,7 +68,6 @@ EOT
 
 mysql <<EOT
 SET GLOBAL innodb_compression_algorithm=lz4;
-SET GLOBAL innodb_compression_algorithm=snappy;
 SET GLOBAL innodb_compression_algorithm=zlib;
 SET GLOBAL innodb_compression_algorithm=none;
 EOT