on some systems, tests may take over an hour to run--only to find
you might have used an unintended Meson version (e.g. release instead
of dev). This change prints the Meson version at the start of the
run_*tests*.py scripts.

Also, raise SystemExit(main()) is preferred in general over
sys.exit(main())

See also #7307 #7314 #7316

cc @nirbheek

Make the expected output check mandatory for failing-meson and warning-meson tests

Unify present or absent test.json file cases in gather_tests

Make expected stdout mandatory in test.json for some test categories

Use a trivial TestCategory class rather than a tuple, to make it easier
to default category attributes

This reverts commit 0871b1032c53287a1ed3ce5108799fb0daccaec5, reversing
changes made to 9dc3ca2c1c9fbb47e731551c6432df144f725261.

Make the expected output check mandatory for failing-meson and warning-meson tests

Unify present or absent test.json file cases in gather_tests

Make expected stdout mandatory in test.json for some test categories

Use a trivial TestCategory class rather than a tuple, to make it easier
to default category attributes