gh-128661: Fix typing.evaluate_forward_ref not showing deprecation

[sobolevn]

Now calling typing.evaluate_forward_ref without type_params raises a warning, as it should.
Calling ForwardRef._evaluate only raises 1 warning, as it should.

I've also covered all branches. After:

No backports are needed, this is 3.14 only feature.

• Issue: typing.evaluate_forward_ref is not fully covered #128661

[JelleZijlstra]

I don't think we should have done this; it makes the interface excessively clunky.

[sobolevn]

@JelleZijlstra what's your opinion about the alternative?

[JelleZijlstra]

The code was correct as is. Forcing people to write type_params=() to handle a rare edge case is not friendly to users.

[sobolevn]

Hm, looks like other similar APIs also has this pattern. Like typing._eval_type and ForwardRef._evaluate.

I got confused by

cpython/Lib/typing.py

Lines 1053 to 1055 in 1b39b50

	if type_params is _sentinel:
	_deprecation_warning_for_no_type_params_passed("typing.evaluate_forward_ref")
	type_params = ()

How can anybody pass _sentinel there, if it is not a default?