Separate safe and unsafe RPC endpoints

[cwgoes]

"Safe" endpoints can be publicly-exposed by a node to untrusted clients (modulo DoS).
"Unsafe" endpoints should not be publicly exposed to untrusted clients.

We also need a distinction for:

• Routes where clients can verify the data returned by untrusted nodes with lite client proofs
• Routes where clients cannot verify the data returned by untrusted nodes.

[cwgoes]

cc @cosmos/cosmos-ui Do you have any thoughts on this? It will probably change routes.

[jbibla]

what will the authentication method look like for trusted clients?

[faboweb]

Which endpoints would change? May also be a good chance to add missing endpoints to the REST server so we only have one source of truth.

[cwgoes]

what will the authentication method look like for trusted clients?

I don't know if we would have one initially; instead probably we'll just emphasize that untrusted RPC servers should only bind to localhost.

[alexanderbez]

No longer needed due to #3641