[ENHANCEMENT] Implement Observations and actions in Pydantic

[burtenshaw]

Observations and actions are currently defined as dataclasses. In general, it's recommend to use Pydantic here. The main benefit is that since the http env is based on Pydantic, we would have auto-validation + auto-generated docs.

Hopefully it's just a drop-in replacement (+update existing envs). It happened to me to pass incorrect data which resulted in HTTP 500, which is not great UX. Other advantage of Pydantic is to generate a jsonschema which could be reused in the web interface to create a form.

[rycerzes]

@burtenshaw you can assign this to me since I wanted to work on updating the existing envs as well :)

[burtenshaw]

Thanks so much @rycerzes ! That would be great.