refactor: convert project to use Firmware Test Builder

Until now, the Firmware Test Builder (FWTB) was included as a part
of the project. This patch removes that part and adds the the FwTB
as a dependency, simplifying the current project and its
responsibilities, focusing only on the unit tests.

Note: due to toolchain compatibility issues, the FDT tests have been
removed in this patch, and will be addressed in a further one.

Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
Change-Id: Id50057d62d1271e0fbd594b418d201bde5fc31d8
14 files changed