Introduces the option security.protectKernelImage that is intended to control
various mitigations to protect the integrity of the running kernel
image (i.e., prevent replacing it without rebooting).
This makes sense as a dedicated module as it is otherwise somewhat difficult
to override for hardened profile users who want e.g., hibernation to work.
This test exercises the linux_hardened kernel along with the various
hardening features (enabled via the hardened profile).
Move hidepid test from misc, so that misc can go back to testing a vanilla
configuration.
