Retrieve Type from typecheck result for type lenses

[berberman]

Closes #1468 and #622

Parsing error messages from GHC would be tricky, so let's render signatures by ourselves, using information from typecheck. I'll add tests later.

[pepeiborra]

Can we have tests for non trivial things like:

1. Polymorphic types
2. Rank-n types and other types with forall
3. Types with identifiers out of scope
4. Types with type operators
5. Types with promoted constructors and literals

We know that GHC error messages can handle all of the above, by definition, but we need to make sure that the solution in this PR can as well.

[berberman]

Is it a new non-deterministic failure?

boot-def-test: FAIL (0.92s)
  test\\exe\\Main.hs:3226:
  number of definitions
  expected: 1
   but got: 0

[Ailrun]

Yeah, it looks so...

[berberman]

This PR is ready for review.