[3.12] gh-117889: Fix PGO test in test_peg_generator (GH-117893) (#117895)

Reuse support.check_cflags_pgo() in test_peg_generator to check for
PGO build.

Log PGO_PROF_USE_FLAG in test.pythoninfo.
(cherry picked from commit 64cd6fc9a6a3c3c19091a1c81cbbe8994583017d)

Co-authored-by: Victor Stinner <vstinner@python.org>