feat: implement generic agent endpoint
What does this merge request do and why?
Add an endpoint that can invoke all of our simple agents.
Part of gitlab-org/gitlab#465858
How to set up and validate locally
Check out the examples at !921
Merge request checklist
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Tests added for new functionality. If not, please raise an issue to follow up. -
Documentation added/updated, if needed.
Edited by Alexander Chueshev