Allow pattern matching on type fields of modules

[christoph-dfinity]

My goal here is to allow importing types in an unqualified manner without having to add an extra binding.

import { type Result } "mo:base/Result";

// instead of

import Result "mo:base/Result";
type Result<Ok, Err> = Result.Result<Ok, Err>

Following up on https://github.com/dfinity/motoko/pull/3362

[rvanasa]

+1 (would've benefited from this dozens of times in various situations). Maybe P3 priority or P2 if we find some compelling use cases?

[christoph-dfinity]

Released in version 0.15.1