Add configuration prototype

[ocelotl]

Move the prototype from [https://github.com/open-telemetry/opentelemetry-configuration/pull/62] to this repo.

[codeboten]

@open-telemetry/python-maintainers hello! i'd like to take on the work to implement a prototype for declarative configuration in Python. What's the best way to do this? Would it be best to take over #3632, or best to start fresh?

One thing I've found helpful in the go implementation was to break things up in smaller PRs to get things moving. Let me know what you would all prefer!