Configure from configuration

### Overview

Allow configuration by network similar to geth provider.

### Specification

Something like this would be cool:

alchemy:
ethereum:
mainnet:
uri: https://eth-rinkeby.alchemyapi.io/v2/API_KEY

Or if you feel strongly about using keys instead of JSON-RPC URIs:

alchemy:
ethereum:
mainnet:
api-key: API_KEY

Or maybe both?

There's probably some security concern here. It's not ideal if these keys are committed to public repos for an Ape project. However, I think that should be a decision for users to make (they may encrypt the config in their worfklow or use private repos and share keys between the team for dev purposes).

### Dependencies

Not a hard dep, but I think this would gel well with a global config: https://github.com/ApeWorX/ape/issues/379.