feat(server): add http endpoint to describe supported parameters for pipeline

[eliteprox]

It would be useful to add an openapi spec formatted endpoint to the pytrickle server so that orchestrators can describe the expected pipeline parameters and request format for the capability.
https://github.com/livepeer/pytrickle/blob/main/pytrickle/server.py

Changes also likely needed to go-livepeer.

[linear]

COMFY-302

[eliteprox]

cc @rickstaa Adding on to your idea, we can do this with other containers too (scope, ai-runner)