Shorten namespace access and create aliases

[Jand42]

• [x] While being inside namespace A, shorten a name like A.B to B.
• [ ] If a B also exists as a global type/value, it is shadowed by A.B inside A. If a value/type would be used anywhere where it's shadowed, create a (non-exported) alias for it type B$1 = B or const B$1 = B. This is not just a cosmetic change but also needed for correct behavior.
• [ ] Create aliases to shorten accesses from imported modules. For example type X = OtherModule.X

[Jand42]

A fix needed: interfaces and class members also have to be considered