Mark calls to oblivious methods in #nullable contexts in Quick Info

[jasonmalinowski]

Right now if you have a piece of code that is #nullable enabled and calls an oblivious method, you don't get any warnings to this effect. This is good because in a mixed codebase if you had compiler warnings this would quickly get really noisy. But, we should probably show some simple hint in Quick Info that lets the user know the call isn't being considered for nullability, so they know where the dragons may still lie.

@333fred's suggestion for the text was "This call is not null aware", which I think is a great wording.

[333fred]

And extend for property/field/etc.

[CyrusNajmabadi]

Closing out due to lack of feedback.

[333fred]

Sorry, I don't think we should close this out. There's plenty of feedback related to it:
#36983
#44063
#42318
#47481

[jasonmalinowski]

Agreed; this is still a common source of feedback.

[CyrusNajmabadi]

Fine to reactivate this. But we should assign a person/milestone and actually ensure we're properly handling this feedback. If it's in the backlog, and untouched for N years, that's effectively us choosing to not do it. Conversing on wednesday on process changes to address this.