Add tool execution unit test for rerun_remapping.
Refactor tool so incoming dict isn't passed to __handle_tool_execute.

Slightly confusing that state params and raw incoming passed to that method, so pull out rerun_remap_job_id sooner and just pass that along (it was the only incoming was used for). Use the oppertunity to isolate potential errors with decoding rerun_remap_job_id and include more informative error message.

Add unit test to test invalid rerun_remap_job_ids.