- Derive TypeFoldable on `hir::place::Place` and associated
  structs, to them to be written into typeck results.

Co-authored-by: Jennifer Wills <wills.jenniferg@gmail.com>
Co-authored-by: Logan Mosier <logmosier@gmail.com>

- final_upvar_tys now reads types from places instead of using `node_ty`

Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>

- This allows us to delay figuring out the index of a capture
  in the closure structure when all projections to atleast form
  a capture have been applied to the builder

Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>

- Use closure_min_capture maps to capture precise paths
- PlaceBuilder now searches for ancestors in min_capture list
- Add API to `Ty` to allow access to the n-th element in a
  tuple in O(1) time.

Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>

- Closures now use closure_min_captures to figure out captured paths
- Build upvar_mutbls using closure_min_captures
- Change logic in limit_capture_mutability to differentiate b/w
  capturing parent's local variable or capturing a variable that is
  captured by the parent (in case of nested closure) using PlaceBase.

Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>

- Use closure_min_captures to generate the Upvar structure that
  stores information for diagnostics and information about
  mutability of captures.