Issue #19714: Tests for importlib.machinery.WindowsRegistryFinder.

Patch by Claudiu Popa, review by Martin v. Löwis.
Issue #22191: Fix warnings.__all__.

Thanks to Jon Poler for the patch.
Merge for issue #22191 fix
Issue #22150: Fix deprecated-removed directive in Sphinx 1.2.
Issue #22150: Fix deprecated-removed directive in Sphinx 1.2.
Issue #20152: Convert _multibytecodecs to Argument Clinic.
Issue #20152: Convert the grp module to Argument Clinic.