feat: Implement experiments REST API (#3411)

* Create datasets feature branch

* Spike out experiment routes

* Add status column to datasets migration

* Spike out experiment runner

* Ruff 🐶

* Add object payloads to experiment responses

* Spike out basic eval flow

* Migration and ORM fixes

* Ensure we default to the latest dataset version

* Always pull examples associated with correct version

* Flush, don't commit

* Clean up experiment creation route and remove experiment "sealing"

* Implement GET experiment route

* Flesh out experiment runs API

* Remove experiments module spike

* Flesh out evaluation route

* Update migration to use trace id instead of trace rowid

* Clean up API and add basic workflow test

* Fix list experiment runs bugs

* Remove unused exceptions

* Don't use `get` for path params

* Remove more "gets" from global id constructions for type clarity

* Remove accidental nullable trace-rowid addition

* Address PR feedback

* Only use get if we have a good fallback