This mostly exist for
- Knowing of the value came from the command-line but we now have
`ArgMatches::source`
- Counting the number of flags but we now have `ArgAction::Count`
`multicall` allows you to have one binary expose itself as multiple
programs, like busybox does. This also works well for user clap for
parsing REPLs.
Fixes#2861
This is a part of #2717
Some settings didn't get getters because
- They are transient parse settings (e.g. ignore errors)
- They get propagated to args and should be checked there
`is_allow_hyphen_values_set` is a curious case. In some cases, we only
check the app and not an arg. This seems suspicious.
