realm: r/sys/networks

[leohhhn]

Description

Superseedes #815

We should create a system realm which would hold official information about chains. This realm will be GovDAO managed, which will allow users and services to get official information about testnets, such as the chainID, chain domain, import domain, etc.

An example usage of this realm could be the following:

r/sys/networks.ByChainID("test5") -> Network{ChainID: "test5", ImportDomain: "test5.gno.land"}
r/sys/networks.ByImportDomain("test5.gno.land")  -> Network{ChainID: "test5", ImportDomain: "test5.gno.land"} 

Later, we could also pair it with another realm, r/sys/nodes, which would be a permissionless realm with rules to which entities could add information about nodes they're running, such as the RPC endpoint, gnoweb endpoints, etc.

Clients such as gnokey could then query this realm to get available endpoints to send transactions to, without having to set the rpc & chainid manually.

cc @moul