Support usage of apt when using fab-investigate

[JedMeister]

Firstly I'm not sure if we already include fab-investigate in the fab package or not? If we don't then we should!

Either way, it would be nice if fab-investigate in a bootstrap/buildroot chroot supported usage of apt OOTB.

apt already "just works" in an appliance chroot - from root.build or later. But on occasion, I like to update a bootstrap or buildroot manually rather than rebuildign from scratch.

To support this use case it should just need to configure a nameserver and apply the bootstrap_apt overlay (from common).

OTOH, perhaps this is a bad idea? I'm open to feedback.

If we do implement this, I suggest that we add a switch so current default behavior is unchanged. We'd also need to remove it when exiting the chroot.