TypeSpec APIView should be moved into monorepo from azure-sdk-tools

`typespec-apiview` was originally created in the `azure-sdk-tools` repo because that is where all other APIView parsers lived. However, there's no actual benefit to having the code live there, and it has happened more than once where a TypeSpec release resulted in breaks to APIView, which immediately begins failing TypeSpec PRs.

EngSys could add checks to make sure typespec-apiview continues to work with typespec-next, but it makes even more sense to simply move the code into the monorepo. It is an emitter just like any other, and including it in the monorepo would ensure that APIView remains compatible with any changes to TypeSpec.