Make more options overridable in pgtest.PGConfig

[TheSalarKhan]

Hi @rubenv

Thanks allot for the amazing library, you might find this cool - maybe slightly concerning 🤣 - but we're using pgtest to spin up temporary databases on the network, to provide quick databases for testing purposes.

tl;dr we simply pipe TCP connections to unix sockets for pgtest instances spun up in real-time.

But we can't do this unless we have predefined passwords/dbnames set (security, its on the network!). And in some instances - for longer running/multi-phase usecases - we need to disable Fsync.

So I've added options to the pgtest.PGConfig config builder, which are used by the core start method to tailor for specific cases.

I have added tests that make sure this works.

Raising this PR in hopes that it unlocks more use-cases for this work of art.

Thanks a ton!

[CodeAshing]

LGTM, Great work @TheSalarKhan

[karelbilek]

I am not a maintainer here at all, but I personally find this a bit out of scope for this project.