doc,ewaol-[bsp,config,distro,tests]: Update EWAOL nomenclature

This patch updates and aligns the nomenclature used for EWAOL components
throughout the repository.

The main changes are:

* Images are consistently referred to according to the target architecture
  (e.g., ewaol-baremetal-image, ewaol-virtualization-image).

* The VMs running on an EWAOL virtualization image are consistently referred to
  Control VM and Guest VM, provided as Xen Dom0 and DomU respectively.

Issue-Id: SCM-3893
Signed-off-by: Richard Neill <richard.neill@arm.com>
Change-Id: Iae24137d394f6dfed5da3090c7f76d6845439cc4