pgsql: Remove most msys special processing in TAP tests

Remove most msys special processing in TAP tests

Following migration of Windows buildfarm members running TAP tests to
use of ucrt64 perl for those tests, special processing for msys perl is
no longer necessary and so is removed.

Backpatch to release 10

Discussion: https://postgr.es/m/c65a8781-77ac-ea95-d185-6db291e1baeb@dunslane.net

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/aa8d4137f990da6949a87cdea49907f3519f5849

Modified Files
--------------
src/bin/pg_ctl/t/001_start_stop.pl   | 11 +----------
src/bin/pg_rewind/t/RewindTest.pm    |  1 -
src/test/perl/PostgresNode.pm        | 15 +--------------
src/test/perl/TestLib.pm             |  6 ------
src/test/recovery/t/cp_history_files |  7 -------
5 files changed, 2 insertions(+), 38 deletions(-)