Use a separate data received handler in VFilterSelect (#19929)

Use a separate data received handler in VFilterSelect (#19929)

Move parts of the request handling to a separate handler
class that keeps track of the current communication state etc.

This is an intermediate change. Later changes should move
waitingForFilteringResponse etc. to the handler.

Change-Id: I762d15cc4b54ead3003e6d9d913e2a975256644c