Map impl block dependencies

[notdanilo]

Considering the following example

impl Person {
  pub fn new(name: FullName, age: Age) -> Self { ... }

  pub fn more_deps(age: Age, a: A, b: B, c: C) -> D;
}

We need a function which returns all the dependencies for the Implementation block with the signature:

impl Implementation {
  pub fn dependencies(&self) -> Vec<Identifier>;
}

where in the example above should return ["FullName", "Age", "A", "B", "C", "D"].

[notdanilo]

Maybe we should transform all the inputs to fully-qualified paths.

[notdanilo]

This won't be needed as we are going to have a proper symbol finding mechanism