Remove cocotb.coroutine and yield syntax

[ktbarrett]

Closes #1967.

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (32b8581) 66.89% compared to head (64f0f43) 66.53%.
Report is 2 commits behind head on master.

Files	Patch %	Lines
src/cocotb/task.py	42.85%	2 Missing and 2 partials ⚠️
src/cocotb/decorators.py	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3509      +/-   ##
==========================================
- Coverage   66.89%   66.53%   -0.36%     
==========================================
  Files          49       49              
  Lines        8457     8429      -28     
  Branches     2384     2378       -6     
==========================================
- Hits         5657     5608      -49     
- Misses       1689     1705      +16     
- Partials     1111     1116       +5     

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[ktbarrett]

#3461 will remove the two lines that aren't covered.

[marlonjames]

Task.__init__() should remove this and let the TypeError be raised, right? The error message on that needs to be cleaned up as well, it still references yield.

cocotb/src/cocotb/task.py

Lines 47 to 48 in 32b8581

	elif inspect.isgenerator(inst):
	self._natively_awaitable = False

I think it's safe to remove the generator support from walk_coro_stack() with this change:

cocotb/src/cocotb/utils.py

Lines 288 to 305 in 32b8581

	def walk_coro_stack(coro):
	"""Walk down the coroutine stack, starting at *coro*.
	Supports coroutines and generators.
	"""
	while coro is not None:
	try:
	f = getattr(coro, "cr_frame")
	coro = coro.cr_await
	except AttributeError:
	try:
	f = getattr(coro, "gi_frame")
	coro = coro.gi_yieldfrom
	except AttributeError:
	f = None
	coro = None
	if f is not None:
	yield (f, f.f_lineno)

And I think a newsfragment is needed for this as well, similar to #3425

[marlonjames]

The only thing left is the TypeError message in Task.__init__(). Now is a good time to update it but it could be left for later cleanup.

        else:
            raise TypeError(
                f"{inst} isn't a valid coroutine! Did you forget to use the yield keyword?"
            )