Manual networking with configuration files

[ianpaul10]

Ref: https://github.com/exo-explore/exo/issues/279

This PR includes the following changes:

• adds manual option to --discovery-module command flag
• adds a new --discovery-config-path command flag to point to a json config file outlining the expected network config
• NetworkTopology python data class to parse the config file
• ManualDiscovery discovery class to connect to other nodes in the network and perform health checks.
• Added tests for NetworkTopology & ManualDiscovery (tried to follow the pattern of the other Discovery classes for tests, not sure if that's sufficient or not)

[ianpaul10]

Thanks for the review! I believe I addressed all of the comments, so it should be ready for re-review whenever you get a chance

[AlexCheema]

lgtm

[AlexCheema]

Merged. Please email [email protected] with your ethereum address for your $200 bounty in USDC.