- Make full contents, also header files, explicit in -dev packages
  https://salsa.debian.org/mariadb-team/mariadb-10.4/-/commit/fb77df0c75422449c32ab1f5f8650a7e9e91091f
- Don't ship private header files at all.
- Ship both libmariadb.pc and maridb.pc.
- Ship mysql_config only as a symlink.
- Keep 'mariadbcheck' as symlink as somebody could have used it already
  https://salsa.debian.org/mariadb-team/mariadb-10.3/commit/d0466f74d543ac574dcd832e081fdc18538f3edd
- The mariadb.pc is the server pkg-config, ship in libmariadbd-dev.
- The client pkg-config is called libmariadb.pc. Ship only it in the client
  library packages.

Use versioned breaks/replaces for mysql* packages we also provide and fix:

  [ERROR] libmariadb-dev conflicts with libmysqlclient-dev files:
    {'/usr/share/man/man1/mysql_config.1.gz', '/usr/share/aclocal/mysql.m4'}
  [ERROR] libmariadb-dev conflicts with libmysqld-dev files:
    {'/usr/lib/x86_64-linux-gnu/libmysqlservices.a'}