This is another attempt to addressed the continual fallout from
5644850620ae, which "improved" the ddb reset command by running shutdown
hooks. This has proven to be fragile, generating recursive panics in
some scenarios. Being able to reset the system successfully from a
panicked state is of plain importance.
So, we attempt to find a compromise.
Split the commands as discussed: 'reset' is restored to its old
behavior, the bare essential invocation of cpu_reset(). Meanwhile,
'reboot' will execute the full kern_reboot() path, with shutdown
handlers.
I am omitting backwards compatibility of the \s flag unless requested.