ewaol-[config,distro]: Introduce ewaol-security distro feaure

The ewaol-security brings the followng EWAOL images customizations:
 - Force password update for each user account after first log in.
 - Appends 'security.scc' to kernel configuration.
 - Appends 'seccomp' to DISTRO_FEATURES.
 - Ensures all relevant packages are configured '--with-libcap[-ng]'
 - Removes ssh 'root' access and 'debug-tweaks' from IMAGE_FEATURES.
 - Appends 'allow-empty-password' to IMAGE_FEATURES, to allow password
   update on first login either over serial or ssh.

Issue-Id: SCM-3905
Signed-off-by: Kamil Dziezyk <kamil.dziezyk@arm.com>
Change-Id: I940770da2d6aa444db2405ead420fed0d1e2dc6b