databases/pgbouncer: Fix config file

• No need to replace pgbouncer.log as the config mentions the absolute path /var/log/pgbouncer/pgbouncer.log now
• No need to replace pgbouncer.pid as the config mentions the absolute path /var/run/pgbouncer/pgbouncer.log now
• References to other files in /etc/ is changed with ${PREFIX}/etc specially pgbouncer.users which had a reference to /etc directory
• No longer requires gsed so removed the BUILD_DEPENDS
• There was a pkg-message.in file which was not called using SUB_FILES; added accordingly

PR: 259474
Approved by: m.tsatsenko@gmail.com (maintainer)
Sponsored by: Bounce Experts