`call` and `chain` meta-commands should take one argument

[arthurpaulino]

This is a rollback. In order to stay consistent/compatible with what the chain-server will do, we want the call and chain meta-commands to only accept one argument for the functional commitment.

While at it, we can also simplify the call expression from ((open hash) arg) to just (hash arg) after #1163 + #1170.