GH-119668: expose importlib.machinery.NamespacePath (#119669)

* GH-119668: expose importlib.NamespacePath

Signed-off-by: Filipe Laíns <lains@riseup.net>

* add news

Signed-off-by: Filipe Laíns <lains@riseup.net>

* add to docs

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Apply suggestions from code review

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

* Fix news (importlib.NamespacePath > importlib.machinery.NamespacePath)

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Link to module.__path__ in NamespacePath docs

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Mention the path argument in the documentation

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Simplify docs text

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Highlight argument names in docs text

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Update Lib/importlib/_bootstrap_external.py

Co-authored-by: Brett Cannon <brett@python.org>

* Rewrite NamespacePath's doc

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Specify path_finder's type in the NamespacePath docstring

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Fix doc tests

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Apply suggestions from code review

Co-authored-by: Barry Warsaw <barry@python.org>

* Fix doc lint

Signed-off-by: Filipe Laíns <lains@riseup.net>

* Update Doc/library/importlib.rst

Co-authored-by: Brett Cannon <brett@python.org>

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Signed-off-by: Filipe Laíns <lains@riseup.net>
Co-authored-by: Brett Cannon <brett@python.org>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Barry Warsaw <barry@python.org>