Silence leakage complaint about postgres_fdw's InitPgFdwOptions.

Silence leakage complaint about postgres_fdw's InitPgFdwOptions.

Valgrind complains that the PQconninfoOption array returned by libpq
is leaked.  We apparently believed that we could suppress that warning
by storing that array's address in a static variable.  However, modern
C compilers are bright enough to optimize the static variable away.

We could escalate that arms race by making the variable global.
But on the whole it seems better to revise the code so that it
can free libpq's result properly.  The only thing that costs
us is copying the parameter-name keywords; which seems like a
pretty negligible cost in a function that runs at most once per
process.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Discussion: https://postgr.es/m/2976982.1748049023@sss.pgh.pa.us