Add contextual method types to Quotes API

[nicolasstucki]

Hmm, interesting... It looks like the compiler internally uses ContextualMethodType rather than just MethodType to express a method with (using ...) parameters clause but currently there seems no way to create contextual methods from the quotes' reflect API. @nicolasstucki are there any plans to add this functionality in the nearest future?

Originally posted by @prolativ in #14056 (reply in thread)

[nicolasstucki]

We should add this.

[rssh]

related old issue: #17663