Support tracking and cancelling long running requests to kai-rpc-server

[sjd78]

Followup to issue #131, and PR #139.

With the synchronous nature of the kai-rpc-server requests, specifically analysis_engine.Analyze and getCodeplanAgentSolution, there is currently no real way to have Kai abort the request without killing the server process. Once the kai-rpc-server supports tracking and aborting long running requests, add the ability to actually cancel an analysis or a get solution request along with unblocking the UI.

This will probably involve using a LSP server style Work Done Progress or Cancellation support. The request would include a generated uuid. Then the server can send messages back with progress notes. Another request from the extension could be made to cancel the operation using the originally generated uuid.

See konveyor/kai#525 for getting the necessary support for this in the server process.