Add locations to high-level types

[pgoodman]

Prerequisites

• [X] I have read the documentation and the proposed feature is not implemented.

Description

High level types have a one-to-one, or near one-to-one mapping with Clang QualTypes or clang::Type *s. Further, clang::Type *s are already subject to deduplication. I would like hl.* types to have the ability to be annotated with location metadata, which would correspond to a request for the location on the corresponding clang::QualType or clang::Type *.

When high-level types are desugared to MLIR built-in types, we should consider these locations lost, as it would be burdensome to wrap all types all the way through the pipeline just to support locations.

[pgoodman]

If #464 is implemented then I will not require this feature.