Add UI to make it easy to see what flows/tasks are currently running on a worker.

[jfloodnet]

First check

• [X] I added a descriptive title to this issue.
• [X] I used the GitHub search to find a similar request and didn't find it.
• [X] I searched the Prefect documentation for this feature.

Prefect Version

2.x

Describe the current behavior

It is not possible to discover what flows are running on a worker, or how many a worker is running.

Describe the proposed behavior

1. Add clear indication on a flow in the UI which worker is running it.
2. Add a filter to filter flows by worker
3. Add nice charts to show statistics about flows per worker.

Example Use

No response

Additional context

No response

[zhen0]

Thanks for the proposal @jfloodnet 🙏