doc,oeqa/cam: Add integration tests for cam-app-example on multiple VMs

Add support for running multiple concurrent commands on different
terminals within the Linux terminal test utility.

Add support for spawning and closing DomU terminals within the
Xen test utility.

Restructure the testsuite into classes. Run the app tests,
calibration, analyze, pack, and deploy on DomU2 as well as DomU1
for virtualization builds.

Add integration tests which test multiple cam-app-example
instances running concurrently on separate VMs. Update the
expected test suite output in the documentation.

Signed-off-by: Debbie Martin <Debbie.Martin@arm.com>