ci: add structured L1 and L2 testing for RMM

Introduce L1 build test to compile only the RMM.
Add L2 test to build TF-A, TFTF, and RMM, and run
the complete stack on the FVP AEM model.

Change-Id: I08c0fdf4d6d37b5d779bf48a47395fbae943931c
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
3 files changed