Feature Request: support `__slots__`

[rchen152]

Describe the Bug

When a class defines __slots__, pyrefly shouldn't allow writing to attributes that aren't specified in __slots__. This is tested in the dataclasses_slots conformance test, which we currently fail:

pyrefly/conformance/third_party/dataclasses_slots.py

Lines 24 to 25 in 47f5efe

	# This should generate an error because "y" is not in slots.
	self.y = 3 # E

Sandbox Link

https://pyrefly.org/sandbox/?code=MYGwhgzhAECCBcAoaLoH00RAewC4Q2gF5oAKAcgA9yAaASmVQBMBTAM3TQEsA7L3DKQgsQbOklSTow0QDpKxaABYATIynSRbWQE9FqlAGJoAFQAWXGBDPYAriCY9yuaACMW0MCBwB3FkyA

(Only applicable for extension issues) IDE Information

No response

[yangdanny97]

I've been thinking about this and __match_args__ which has similar properties.

I was thinking we should try and compute these while solving class metadata and store it as something better than Type::Tuple([Type::Literal(...), Type::Literal(...)].

[Adist319]

I can take a look at this!

[rchen152]

Assigned, thank you!

[Adist319]

PR created here: #2029