Add code coverage and visualization

* Add code coverage build and test.
* Add coverage report and visualization.

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>