build_helpers: Add TC3 test with CCA Attestation scheme

Add TC3 test with CCA attestation scheme, while the default
for the platform is now DPE.
Only perform the NS regression test to save resources, as the
S regression test is covered with the default attestation.

Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Change-Id: I7f9a70bf9a57ed4983119b304388ed4c2a1594c6
2 files changed