[memory refactor][6/n] Update naming and routes (#839)

Making a few small naming changes as per feedback:

- RAGToolRuntime methods are called `insert` and `query` to keep them
more general
- The tool names are changed to non-namespaced forms
`insert_into_memory` and `query_from_memory`
- The REST endpoints are more REST-ful

llama_stack/apis/vector_io/vector_io.py

@@ -38,7 +38,7 @@ class VectorDBStore(Protocol):
 class VectorIO(Protocol):
     vector_db_store: VectorDBStore
 
-    # this will just block now until documents are inserted, but it should
+    # this will just block now until chunks are inserted, but it should
     # probably return a Job instance which can be polled for completion
     @webmethod(route="/vector-io/insert", method="POST")
     async def insert_chunks(