Make reloadable TLS system variables dynamic

With MDEV-16266 implemented in 10.4, it seems like we have an opportunity to make certain SSL/TLS system variables dynamic.

It looks like FLUSH SSL uses the following variables to reload the TLS context:

• ssl_cert
• ssl_key
• ssl_ca
• ssl_capath
• ssl_crl
• ssl_crlpath
• ssl_cipher

https://github.com/MariaDB/server/blob/mariadb-10.4.4/sql/mysqld.cc#L4735

https://github.com/MariaDB/server/blob/mariadb-10.4.4//vio/viosslfactories.c#L334

Can all of these variables be made dynamic in 10.4, as long as the system supports FLUSH SSL?