Add FVP run and combine coverage

* Run full Linux in FVP to test features without silicon.
* Collect coverage report from multiple runs.

Signed-off-by: Viet-Hoa Do <viet-hoa.do@arm.com>

Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Approved-by: Jakub Sujak <jakub.sujak@arm.com>