Fallback Web3, IPFS endpoints

[leovigna]

Enable a multi-endpoint configuration, enabling Web3-Redux to rely on multiple endpoints (eg. Infura, Alchemy, Local node) for Web3 RPC and IPFS connections. This effectively enables a client-side load balancer.

• Network add web3Fallbacks
• IPFS add ipfsUriFallbacks
• Update all relevant sagas accordingly to use fallbacks when needed

It is possible to implement 2 distinct behaviours for using the fallbacks:

• Error/Timeout only: Try fallback connections one after the other if an error occurs or a request takes too long.
• Concurrent Requests: fallbacks are used alongside the primary connection and the first response is used to update the local state. Subsequent requests can be used to asses the validity of the initial response and handle conflicts accordingly.