Re: [oauth] Split and extend PGOAUTHDEBUG

Thanks for the review, these changes generally sound good.

> I think `fast-retry` needs to be moved under UNSAFE and renamed to
> something that doesn't sound "good". `dos-interval` maybe?

I would use a different name, for something like `dos-interval` I
would expect to provide a time since it's an interval?
`immediate-retry` maybe? Or `dos-retry`?

> nitpick: `poll-counts` and `print-plugin-errors` choose different
> naming conventions, and we're not referring to the poll() API for the
> former. `call-count`? `dlopen`?

I didn't want to write "print-poll-counts" and "print-trace" as those
are just longer, while simply writing "plugin-errors" without print
also seemed wrong. Maybe it could be "plugin-debug" instead, that
sounds good even withour print?

> I have a sample patch locally for these suggestions, if you'd like.

I can create a patch with these updates tomorrow, but if you already
have it, that might be easier/quicker.

> I'm not a fan of 0002

That's okay, I am fine with dropping that. We are already using that
small custom libpq client for testing, so we can keep using it. I just
thought this could make things easier/clearer to others.