Create global application event bus

[aloknerurkar]

We should create a global event bus package for mev-commit which can allow different packages to publish and subscribe to events. For eg:

• Peer disconnections
• Provider slashes for provider node as well as other bidder nodes
• Rewards
• Failed storing/opening commitments

Different sub-systems need to react to different events. So having a global event bus is a cleaner design than to do this specific to packages. This event bus can also be used to provide a new API for users to see these events in their infrastructure also.

For eg, provider slashing beyond certain point should lead to bidders re-configuring the encryption key and disconnecting from the provider. Also, currently if we fail to store commitment, there is no feedback for the provider nodes. This can happen due to balance being low or issues with the RPC endpoint. Both need to be addressed. The new API can allow users to see these events as well as other packages to react.