[3.15] gh-86533: Restore os.makedirs() ability to apply *mode* recursively (GH-150011...

[3.15] gh-86533: Restore os.makedirs() ability to apply *mode* recursively (GH-150011) (#150036)

bpo-42367: Restore os.makedirs() and pathlib.mkdir() ability to apply *mode* recursively via a new parent_mode= keyword argument.
(cherry picked from commit 9770e32ce07110f0c8c7a381604ec9a490028eed)

+ Make Path.mkdir parent_mode tests umask-independent

test_mkdir_with_parent_mode, test_mkdir_parent_mode_deep_hierarchy and
test_mkdir_parent_mode_same_as_mode assert exact directory mode bits but
did not pin the process umask.  On buildbots running with a restrictive
umask (e.g. 0o077) the 0o755 leaf was masked down to 0o700, failing the
assertions.  Wrap them in os_helper.temp_umask(0o022), matching the
other umask-aware mkdir tests in this file.

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Co-authored-by: nessita <124304+nessita@users.noreply.github.com>
Co-authored-by: Zackery Spytz <zspytz@gmail.com>
Co-authored-by: Erlend E. Aasland <erlend@python.org>
Co-authored-by: Gregory P. Smith <greg@krypto.org>