When fetching a list of tests for a given extension in contrib/ or
src/test/modules/, NO_INSTALLCHECK now gets checked first.  If present,
an empty list of tests is returned to let the caller know that tests
for this module need to be bypassed.

This actually fixes a set of issues with MSVC with modules using
REGRESS_OPTS, as an incorrect parsing caused the launched command
to eat the first test listed.  The actual effect on the tree is that
several modules listed a single test, so regressions have been running
with no actual tests.  pg_stat_statements, test_rls_hooks and commit_ts
were impacted by that.  Some other modules like test_decoding (or
snapshot_too_old) don't use yet PGXS rules, but their makefiles will
soon be refactored with an upcoming patch.

Author: Michael Paquier
Reviewed-by: Andrew Dunstan
Discussion: https://postgr.es/m/20181126054302.GI1776@paquier.xyz