[PP-1] Introduce a StatementBase abstract class

Not ready yet.

Ready for review - thanks!

Thanks @daffie for your review. Fixed your points and answered your question.

I have refreshed 📌 Create the database driver for MySQLi for async queries Active MR!11355 with the latest changes here - I suggest when reviewing this also seeing that one for how a new implementation of this looks.

I have reviewed the code changes and they look good.
My question has been answered.
There is already a lot of testing in core.
The change for a BC break is very small. Very unlikely.
For me it is RTBC.

This looks good to me, couldn't find anything to complain about. Committed/pushed to 11.x, thanks!

catch → closed merge request !10263