Feature Request - agent details/activity API

[dustymc]

Is your feature request related to a problem? Please describe.

The data needed for #7356 are about the same data needed for /agent/ pages, and it's very complex code (agents are everywhere in Arctos).

Describe what you're trying to accomplish

reuse code

Describe the solution you'd like

agent activity API

Describe alternatives you've considered

There are none, @mkoo is going to ask for this anyway....

Additional context

#7352

Priority

Not terribly high, the duplicate agent notification script can run with only collectors and transaction agents for a while.

Various things (different UI, adding download capacity, etc.) might change things.

Going next task, I know how to do this.