actions: run: add support for running commands outside of fakemachine

[silbe]

Even when set to run outside the chroot, scripts/commands are still run inside fakemachine. Lots of things don't work within that environment, e.g. because regular /etc is not available (not even sudo works). It would be very useful to have the ability to run scripts outside of fakemachine (as the user invoking debos) with the ability to modify the rootfs.

My particular use case is installing SSH host keys. The keys are encrypted to a private key on an OpenPGP card, accessible to the user running debos. The SSH host keys can only be decrypted by running a command as the original user, not but running within fakemachine or running as root. Additionally they are stored within Salt (Configuration Management system), not just a file encrypted directly with GnuPG. Extracting them requires running a command within the regular environment of the user.