Drops PG14 support

[naisila]

DESCRIPTION: Drops PG14 support

1. Remove "$version_num" != 'xx' from configure file
2. delete all PG_VERSION_NUM = PG_VERSION_XX references in the code
3. Look at pg_version_compat.h file, remove all _compat functions etc defined specifically for PGXX differences
4. delete all PG_VERSION_NUM >= PG_VERSION_(XX+1), PG_VERSION_NUM < PG_VERSION_(XX+1) ifs in the codebase
5. delete ruleutils_xx.c file
6. cleanup normalize.sed file from pg14 specific lines
7. delete all alternative output files for that particular PG version, server_version_ge variable helps here

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-13.0@b29ecd1). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff               @@
##             release-13.0    #7753   +/-   ##
===============================================
  Coverage                ?   89.59%           
===============================================
  Files                   ?      274           
  Lines                   ?    59414           
  Branches                ?     7422           
===============================================
  Hits                    ?    53231           
  Misses                  ?     4055           
  Partials                ?     2128           

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