filter_dbs - Run takes a long time due to a lot of databases and tables

[visch]

Thread: https://meltano.slack.com/archives/C01TCRBBJD7/p1692197784713329

When your mysql instance has a lot of DB's and tables you may only want to pull from one of the databases as right now it's taking >5 min for this user to run discovery due to https://github.com/meltano/sdk/blob/main/singer_sdk/connectors/sql.py#L499-L513

[jlloyd-widen]

FWIW, I created a version of this tap and ran into this exact problem. I found a way to speed it up. It's probably very ugly. But in case any of the code is useful or instructive, please feel free to use.