Add a function to find `Name` from `OrigName`

[yav]

This would be handy for a few reasons:

• We could probably avoid having PrimMap to resolve "wired-in" syntac
• It would be handy to have in verification contexts where one may want to refer to things that are not necessarily in scope or exported (e.g., when using Cryptol from SAW, or running test via the Python API)

Since the original name contains the path of modules and the indentifer, and each module should only define one thing
with a particular name, this should be fairly straight forward.

Another benefit of having this function and using it is that it would further test that the original names for things are correct,
as they are not heavy used at present...