Added TypeName and TypeUsage from OpenAPI Generator. (#1726)
Motivation:
The types are used by the code renderer that will be brought over from OpenAPI Generator
to the new gRPC Swift CodeGenLib.
Modifications:
Copied the TypeName, TypeUsage and some TypeName extensions that will be used
in the context of gRPC, and modified TypeName so it represents only the Swift path
of a type.
Result:
We will be able to bring over the Code Renderer and we will have types representations that can be used
by the service translator.
Stefana-Ioana Dranca