Update localHost RPC object to support multiple networks

[Mi-Lan]

Is your feature request related to a problem? Please describe.
Currently when we select alternative rpc via rpc modal it is saved for just that network on local storage and current object looks like this

And the problem with that is that it will be overwritten if you save alternative rpc on different chain. So that means it only supports one chain.

Describe the solution you'd like
We should expand localHost rpc object to be able to save alternative rpcs on multiple chains and not overwrite chain saved after we set it for different network.