[docs] Add docstrings to CLI

[exdx]

Currently the CLI is undocumented -- it would be helpful to users if some docstrings were present. We can start at the top-level sub-commands and go deeper into specific commands afterwards.

A/C: Add docstrings to top level mfi commands:

SUBCOMMANDS:
    account
    bank
    group
    help                        Print this message or the help of the given subcommand(s)
    inspect-padding
    inspect-size
    inspect-switchboard-feed
    lip
    patch-idl
    profile