Support server version detection for MSSQL+MySQL

### What problem are you facing?
In [749c80a](https://github.com/crossplane-contrib/provider-sql/commit/749c80a) we added the ability to filter privileges based on PostgreSQL server version (e.g., the `MAINTAIN` privilege is only available in PG 17+).

The reconcilers call `GetServerVersion()` during `Connect()` and pass the version to privilege expansion functions.

Both MySQL and MSSQL had `GetServerVersion` added to satisfy the `xsql.DB` interface, but the implementations were no-ops.

### How could Crossplane help solve your problem?
Real `GetServerVersion` implementations to allow a similar experience for MSSQL and MySQL.