Offer quick fix for some uses of 'await' outside an async context

[rbuckton]

Originally discussed in #38483.

We currently offer a quick fix to add an async modifier if we parse await in a non-async context when the await is unambiguously an AwaitExpression:

However, we do not offer that quick fix if we parse await in cases where it is ambiguous (such as in a call expression):

We should consider special-casing the error message for await when it is ambiguous so that we can offer compatible quick fixes.

[a-tarasyuk]

@DanielRosenwasser @rbuckton Should it be done in suggestionDiagnostics?

[DanielRosenwasser]

I think the idea is that instead of Cannot find name 'await'. we would possibly issue a special-cased diagnostic like

Cannot find name 'await'. Did you mean to write this in an async function?

and provide a quick fix for that.

[a-tarasyuk]

@DanielRosenwasser Ok, thanks

[DanielRosenwasser]

Thanks @a-tarasyuk!

[a-tarasyuk]

@DanielRosenwasser Not at all :).