As part of the code completion redesign this new entry point is going
to replace use of:

- `typeCheckExpression`
- `getTypeOfExpressionWithoutApplying` (which could be removed)

and possibly other methods currently used to retrieve information
for code completion purposes.

Advantages of a new approach:

- Avoids mutating AST;
- Allows to avoid sub-expression type-checking;
- Allows code completion access to multiple solutions in ambiguous cases;
- Provides all possible solutions - valid and invalid (with holes);
- Allows code completion to easily access not only types but
  overload choices and other supplimentary information associated
  with each solution.