feat: tftf realm extension

This patch adds Realm payload management capabilities to TFTF
to act as a NS Host, it includes creation and destruction of a Realm,
mapping of protected data and creation of all needed RTT levels,
sharing of NS memory buffer from Host to Realm by mapping of
unprotected IPA, create REC and auxiliary granules, exit Realm
using RSI_HOST_CALL ABI.

Older realm_payload name is used now for only R-EL1 test cases,
RMI and SPM test cases have been moved to new file tests-rmi-spm.

New TFTF_MAX_IMAGE_SIZE argument added to FVP platform.mk,
as an offset from where R-EL1 payload memory resources start.

Signed-off-by: Nabil Kahlouche <nabil.kahlouche@arm.com>
Change-Id: Ida4cfd334795879d55924bb33b9b77182a3dcef7