Combine/merge IRascalFileSystemServices and VSCodeUriResolverServer #866
Description
Right now there exists 2 separate URIRegistry over jsonrpc implementations. VSCodeUriResolverServer for exposing VS Code VFS to rascal, and IRascalFileSystemServices for exposing Rascal VFS to VS Code.
They are both written with the source interface in mind. So VSCodeUriResolverServer follows URIResolverRegistry pattern, while IRascalFileSystemServices follows VS Code file system abstraction.
If we would merge these two interfaces, we can have less duplication and less confusion of where what is happening.
I propose we migrate/merge to the VSCodeUriResolverServer as that closer mimics rascal's own filesystem abstraction.