unwrap type assist

[Veykril]

An assist that "unwraps" a type into its generic type argument, that is Option<T> becomes T.

Requirements should be that the type is a path type which exactly one type paramater (and maybe 0+ const and lifetime parameters which are then discarded).

[vishruth-thimmaiah]

@rustbot claim

[snprajwal]

Interesting, looks like "addresses #XXX" isn't a recognised keyword for GitHub to auto-close linked issues.