pgsql: Add authentication TAP test for peer authentication

Add authentication TAP test for peer authentication

This commit introduces an authentication test for the peer method, as of
a set of scenarios with and without a user name map.  The script is
automatically skipped if peer is not supported in the environment where
this test is run, checking this behavior by attempting a connection
first on a cluster up and running.

Author: Bertrand Drouvot
Discussion: https://postgr.es/m/aa60994b-1c66-ca7a-dab9-9a200dbac3d2@amazon.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f60eb3f2827db292edf71bb7296fbdf5958ace3d

Modified Files
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src/test/authentication/meson.build   |   1 +
src/test/authentication/t/003_peer.pl | 102 ++++++++++++++++++++++++++++++++++
2 files changed, 103 insertions(+)