[MISC] Set Pgbackrest spool dir to archive mount

[dragomirp]

Set Pgbackrest spool dir to the archive mount, so that the mount is used for transient restore usage

Checklist

• I have added or updated any relevant documentation.
• I have cleaned any remaining cloud resources from my accounts.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.29%. Comparing base (a179e9d) to head (c5e36b4).

Additional details and impacted files

@@           Coverage Diff            @@
##           16/edge    #1016   +/-   ##
========================================
  Coverage    70.28%   70.29%           
========================================
  Files           16       16           
  Lines         3806     3807    +1     
  Branches       545      545           
========================================
+ Hits          2675     2676    +1     
  Misses        1001     1001           
  Partials       130      130           

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[delgod]

Please excuse me, I was wrong, we need to put the spool dir to the same volume as WAL dir, but not inside WAL dir.