Use monitoring-bus directly for ExecutedActionMetadata metrics

Description

This MR switches the publishing of metrics relating to ExecutedActionMetadata metrics to have the scheduler do the publishing directly using the singleton monitoring_bus. This simplifies the logic and allows removing some methods used only for this purpose out of scheduler.py and server.py, and is consistent with how we publish other metrics.

In addition, I added two new metrics related to ExecutedActionMetadata that were missing:

• Total time spend in the worker
• Time Action spend in queue (we only calculated the average previously)

There don't appear to be any existing tests that touch this part of the code, but if there's a good way to test that metrics are published I'd be more than happy to add some tests.