Update for changes in annotations with Python 3.14

[antoinevg]

Python 3.14 introduces deferred evaluation of annotations (PEP 649 and PEP 749).

Code that relies on manipulating the __annotations__ attribute directly needs to, instead, make use of annotationlib and the get_annotations() function called with the format=Format.FORWARDREF argument.

In this PR we'll use the typeextensions library which provides a backward-compatible implementation for versions of Python <3.14.

More information: https://docs.python.org/3/whatsnew/3.14.html#whatsnew314-porting-annotations

--
Closes #172

[miek]

Sorry about the delay. We have chatted about some of this but just to get some notes written down:

I found that running the unit tests with python -m unittest fails after this change, with:

======================================================================
ERROR: test_code_generation (test.test_descriptors.TestDescriptors.test_code_generation)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/mike/repos/facedancer/test/test_descriptors.py", line 102, in test_code_generation
    new_device = Device()
                 ^^^^^^^^
  File "<string>", line 20, in __init__
  File "/home/mike/repos/facedancer/facedancer/device.py", line 164, in __post_init__
    for configuration in instantiate_subordinates(self, USBConfiguration):
  File "/home/mike/repos/facedancer/facedancer/magic.py", line 129, in instantiate_subordinates
    yield member(object)
          ^^^^^^^^^^^^^^
  File "/home/mike/repos/facedancer/facedancer/magic.py", line 64, in __call__
    return self._target_type(parent=parent)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<string>", line 10, in __init__
  File "/home/mike/repos/facedancer/facedancer/configuration.py", line 111, in __post_init__
    for interface in instantiate_subordinates(self, USBInterface):
  File "/home/mike/repos/facedancer/facedancer/magic.py", line 129, in instantiate_subordinates
    yield member(object)
          ^^^^^^^^^^^^^^
  File "/home/mike/repos/facedancer/facedancer/magic.py", line 64, in __call__
    return self._target_type(parent=parent)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<string>", line 14, in __init__
  File "/home/mike/repos/facedancer/facedancer/interface.py", line 88, in __post_init__
    for descriptor in instantiate_subordinates(self, USBDescriptor):
  File "/home/mike/repos/facedancer/facedancer/magic.py", line 129, in instantiate_subordinates
    yield member(object)
          ^^^^^^^^^^^^^^
  File "/home/mike/repos/facedancer/facedancer/magic.py", line 64, in __call__
    return self._target_type(parent=parent)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: Device.Configuration_1.Interface_0.Descriptor_0x24_A.__init__() missing 1 required keyword-only argument: 'raw'

I think that this change isn't actually keeping the same behaviour as before. Previously, it was adding to the __annotations__ element in classdict passed to the new class, but the new change is only accessing the base-class annotations and not updating anything in the child class.

Also, I think the warnings against manipulating __annotations__ directly apply to existing classes, not during class creation like this. I didn't get far enough into finding the right way to do it, but there's a relevant-looking example here: https://docs.python.org/3/library/annotationlib.html#using-annotations-in-a-metaclass