Read worker information in load_fnc and request_fnc

[longcw]

For some use cases, we want to determine the workload based on the activate jobs in the worker. For now the only way to do this is to modify the run_worker in cli to create a Worker first then manually replace the opts.load_fnc and opts.request_fnc.

Maybe adding a worker arg to these two methods is not a good idea, I wonder if we can make cli.run_app accept a "before_run_hook" that takes worker as input to modify these methods in that hook.