Decouple from Ai2-specific vendors

This project powers asta-autodiscovery.allen.ai where a number of specific cloud providers have been selected for Ai2's needs. To make this codebase more portable and adaptable to arbitrary environments, these cloud-specific implementations need to be abstracted and replaced with low/no-barrier default options.

* [x] Authentication - Abstract to three stock implementations: Auth0, password file, no auth (local mode, new default)
* https://github.com/allenai/asta-autodiscovery/pull/29
* [x] AutoDiscovery jobs - Abstract to two stock implementations: GCP Cloud Run, docker containers (new default)
* https://github.com/allenai/asta-autodiscovery/pull/30
* [x] Code execution sandboxing - Enable configuration of backends supported by https://pypi.org/project/asta-sandbox/ on which this project depends.
- https://github.com/allenai/asta-autodiscovery/pull/56
* [x] LLM providers #68
* [ ] Persistence - Abstract to two stock implementations: GCS, docker host mount (new default)
* [ ] Compute credit tracking - Option to disable, which will become the default. Maybe abstract an interface so 3rd-party operators can implement their own bookkeeping.
- 7/23 plan: organize asta integration code into asta subpackages. Option to disable UI elements. Backend balance checks either disabled, or satisfied by "infinite" credits, whichever solutions is more elegant, fewer unique code paths/LoC.
* [ ] Enable public repo integration tests - a lot of tests don't run because they depend on private infra but after this point all(?) will be runnable using various local, non-cloud components
* [ ] #54
* [ ] AutoDiscovery -> Asta DataVoyager integration - Agent-to-agent handoff is critical to research workflows, but how can we rationalize this from a systems point of view when Ai2 isn't the operator of both agent systems in that exchange?
* [ ] isolate asta-specific integration points in asta-specific subpackages
* ... probably others