Test PGSM with multiple extensions loaded in the server.

[Naeem-Akhter]

Added a tap test case to load multiple extensions in the server before running a test load.

1. We load and create other extensions that are distributed by Percona in PPG. (postgis, pg_repack, pgaudit, pgaudit_set_user, pgpool)
2. Run test data with pgbench.

To make the above test case work, updated the workflows to install above mentioned extension where we use installed packages from PPG. On workflows where we build server or use packages from PGDG, we are skipping this test case.

Also removed the workflows for postgres 11, as it is already EOL.

Updated README.md to add pg-16 and remove pg-11.

[codecov[bot]]

Codecov Report

Merging #429 (aed6fdc) into main (823bfb9) will decrease coverage by 0.01%. Report is 3 commits behind head on main. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #429      +/-   ##
==========================================
- Coverage   90.70%   90.70%   -0.01%     
==========================================
  Files           3        3              
  Lines        1270     1269       -1     
  Branches       35       35              
==========================================
- Hits         1152     1151       -1     
  Misses         96       96              
  Partials       22       22              

see 1 file with indirect coverage changes

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