Fix the following Breaks/Replaces errors detected by Salsa-CI:

  [ERROR] mariadb-server-10.5 conflicts with mysql-client-core-8.0 files:
    {'/usr/bin/myisam_ftdump', '/usr/share/man/man1/myisam_ftdump.1.gz'}
  [ERROR] mariadb-server-10.5 conflicts with mysql-server-core-8.0 files:
    {'/usr/share/man/man1/mysqlbinlog.1.gz',
     '/usr/share/man/man1/myisamlog.1.gz',
     '/usr/share/man/man1/mysql_tzinfo_to_sql.1.gz',
     '/usr/share/man/man1/perror.1.gz',
     '/usr/share/man/man1/myisampack.1.gz',
     '/usr/bin/mysqld_safe', '/usr/share/man/man1/myisamchk.1.gz',
     '/usr/bin/myisamchk', '/usr/bin/mysql_secure_installation',
     '/usr/bin/mysqld_multi', '/usr/bin/mysql_tzinfo_to_sql',
     '/usr/bin/perror', '/usr/share/man/man1/mysqld_multi.1.gz',
     '/usr/bin/myisampack', '/usr/share/man/man1/mysqld_safe.1.gz',
     '/usr/bin/myisamlog',
     '/usr/share/man/man1/mysql_secure_installation.1.gz',
     '/usr/bin/mysqlbinlog'}
  [ERROR] mariadb-test conflicts with mysql-server-core-8.0 files:
    {'/usr/lib/mysql/plugin/adt_null.so',
     '/usr/lib/mysql/plugin/mypluglib.so'}

Upstreamed from Debian packaging commits:
https://salsa.debian.org/mariadb-team/mariadb-10.5/-/commit/9b6a67b53c2adf1bb5497d8649eb079767419835
https://salsa.debian.org/mariadb-team/mariadb-10.5/-/commit/f6d5545a0241de2cda81c878a157517b83378c04

Also:
- remove excess '<< ${source:Version}' on mysql-client-* and mysql-server-*
- move more packages to Conflicts as it is semantically more correct than
  having those packages in Replaces