Update MySql driver to v8.0, remove 5.1

[jmf-tls]

According to the MySql support team, 8.0 doesn't have this bug. So are we planning to not support 5.1 anymore?

I checked, and it doesn't have the bug. We are not currently using MySQL, but I we should keep support in PDB, I guess... We could split this into a PDB API module and then implementation modules, that way we could have a mysql5 and a mysql8, each with a different driver version and different capabilities. Or we could bump the driver version, adjust the code, and release a major version.

MySql 5.7 EOL will be next year(October 21, 2023) so maybe we could just support it until then and after just support 8.0

Originally posted by @upsidedownsmile in https://github.com/feedzai/pdb/issues/299#issuecomment-1042436092