res/res_config_pgsql.c: Use PQescapeStringConn for escaping names.

Use function PQescapeStringConn for escaping the name of the table and
schema instead of doing it manually.

ASTERISK-25132 #close
Reported By: Rodrigo Ramírez Norambuena <decipher.hk@gmail.com>

Change-Id: I302a263f7210d20925f14716b508b081998b7608