clean up pid_t printing and get rid of pgpid_t

On 04.10.22 10:15, Peter Eisentraut wrote:
> I wanted to propose the attached patch to get rid of the custom pgpid_t
> typedef in pg_ctl.  Since we liberally use pid_t elsewhere, this seemed
> plausible.
>
> However, this patch fails the CompilerWarnings job on Cirrus, because
> apparently under mingw, pid_t is "volatile long long int", so all the
> printf placeholders mismatch.  However, we print pid_t as %d in a lot of
> other places, so I'm confused why this fails here.

I figured out that in most places we actually store PIDs in int, and in
the cases where we use pid_t, casts before printing are indeed used and
necessary. So nevermind that.

In any case, I took this opportunity to standardize the printing of PIDs
as %d. There were a few stragglers.

And then the original patch to get rid of pgpid_t in pg_ctl, now updated
with the correct casts for printing. I confirmed that this now passes
the CompilerWarnings job.