Add support for PG15. Disable JIT for monitoring user

[keithf4]

Description

Add support for PG15. Not including pg_stat_statements_full query at this time.

Disable JIT for the monitoring user to avoid suspected memory leak issue found with backrest query

Remove double dollar escape from postgres_exporter systemd service file

Fixes #301 #296 #295 #182

Type of change

Please check all options that are relevant

• Bug fix (change which fixes an issue)
• Feature (change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update only

How Has This Been Tested?

Tested Configuration:

• Ansible, Specify version(s):
• Installation method:
  • Binary install from source, version:
  • OS package repository, distro, and version:
  • Local package server, version:
  • Custom-built package, version:
  • Other:
• PostgreSQL, Specify version(s):
• docs tested with hugo version(s):

Tested with playbook(s):

Checklist:

• My changes generate no new lint warnings
• I have made corresponding changes to:
  • the documentation
  • the release notes
  • the upgrade doc

[hunleyd]

are we doing changelog fragments in pgM?

[keithf4]

are we doing changelog fragments in pgM?

I'm game. Want to add all the necessary bits to this repo? I'll add fragments to my PRs then