core: allow result variadic inference

[alexarice]

Sort of a revert of #3416, but I believe this fixes the underlying problem.

Changes range constraint inference so that passing in a length is optional. The rationale for this is that the length of operands is always known, but the length of results is never known (as they can always be omitted). Similarly updates the can_infer function.

Probably needs a test of something. 🤷

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.40%. Comparing base (52431ee) to head (2f0dd23).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3559    +/-   ##
========================================
  Coverage   90.39%   90.40%            
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  Files         466      466            
  Lines       58642    58760   +118     
  Branches     5585     5599    +14     
========================================
+ Hits        53009    53121   +112     
- Misses       4202     4203     +1     
- Partials     1431     1436     +5     

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[superlopuh]

At the call site, the True or False don't communicate much in terms of what's going on, how do you feel about making the argument mandatory?

Suggested change

	def can_infer(self, var_constraint_names: Set[str], length_known: bool) -> bool:
	def can_infer(self, var_constraint_names: Set[str], *, length_known: bool) -> bool:

[alexarice]

absolutely, I might do the same for infer?

[superlopuh]

Very very nice

[alexarice]

I'm think I'm going to add a test that shows that trying to infer a var_result_def(IntegerType(64)) fails, then this should be good to go