[codeview] Remove TypeServerHandler and PDBTypeServerHandler

Summary:
Instead of wiring these through the CVTypeVisitor interface, clients
should inspect the CVTypeArray before visiting it and potentially load
up the type server's TPI stream if they need it.

No tests relied on this functionality because LLD was the only client.

Reviewers: ruiu

Subscribers: mgorny, hiraditya, zturner, llvm-commits

Differential Revision: https://reviews.llvm.org/D35394

llvm-svn: 308212