Document the public `multiprocessing.[Bounded]Semaphore.get_value` method and refactor code

[YvesDup]

Feature or enhancement

Proposal:

This improvement is based on @ronaldoussoren's comment at #125829 (comment)

1. This public method should be documented in the synchronization primitives of multiprocessing module.
2. I also suggest to refactor code with this public method, in replacement of calls to the private method semaphore._semlock._get_value in the following locations:

cpython/Lib/multiprocessing/synchronize.py

Line 142 in 0c26dbd

value = self._semlock._get_value()

cpython/Lib/multiprocessing/synchronize.py

Line 158 in 0c26dbd

value = self._semlock._get_value()

cpython/Lib/multiprocessing/synchronize.py

Lines 250 to 251 in 0c26dbd

	num_waiters = (self._sleeping_count._semlock._get_value() -
	self._woken_count._semlock._get_value())

cpython/Lib/multiprocessing/queues.py

Line 124 in 0c26dbd

return self._maxsize - self._sem._semlock._get_value()

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-133146: Add the old public get_value method to documentation and refactor code. #133301
• [3.14] gh-133146: Add the old public get_value method to documentation and refactor code. (GH-133301) #142110

[YvesDup]

Perhaps there was a good reason for never documenting this public method.