support utf8mb3 char encoding fully for mysqlclient, others

support utf8mb3 char encoding fully for mysqlclient, others

Fixes to accommodate for the MariaDB 10.6 series, including backwards
incompatible changes in both the mariadb-connector Python driver as well
as the native 10.6 client libraries that are used automatically by the
mysqlclient DBAPI.  The "utf8mb3" encoding symbol is now reported by
these client libraries when the encoding is stated as "utf8", leading to
lookup and encoding errors within the MySQL dialect that does not expect
this symbol.   Updates to both the MySQL base library to accommodate for
this utf8mb3 symbol being reported as well as to the test suite.
Thanks to Georg Richter for support.

Fixes: #7136
Fixes: #7115
Change-Id: I655d9d9868aef76037023d0c602b8a7c881780b0
(cherry picked from commit f43e65f9b557b2d110141137a0216c661ba038b4)