Expose a minimal type parser to dialects.

Expose a minimal type parser to dialects.

This CL exposes a parseType method which allows standalone reuse of the MLIR type parsing mechanism. This is a free function for now because the underlying MLIR parser is not guaranteed to receive a StringRef which lives in the proper MemBuffer. This requires building a new MemBuffer/SourceMgr and modifying the Parser constructor to not require an mlir::Module.

The error diagnostic emitted by parseType has context limited to the local string.
For now the dialect has the additional option to emit its own extra error that has the FileLineColLoc context.

In the future, both error messages should be combined into a single error.

PiperOrigin-RevId: 252468911