-Wincomplete-uni-patterns should not warn about explicitly-marked irrefutable patterns

It is very useful to catch accidentally partial uni-pattern matches:

Cons x = someVal

However, we explicitly want an irrefutable pattern match:

Vector2 0 y = Vector2 0 a op Vector2 0 b

In this case, it would be really useful to opt out of the warning via:

~(Vector2 0 y) = ...

The fact the match is partial is explicit and visible with the ~ syntax, so the warning shouldn't tell us about it.

Right now this warning rules out this useful way of opting in to partiality.

Trac metadata

Trac field	Value
Version	8.2.2
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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