ArmVirtPkg: Add library for Arm CCA helper functions

Introduce ArmCcaLib library that implements helper
functions to:
- probe if the code is executing in a Realm context
- configure the protection attribute in page tables
  for the memory regions shared with the host
- get the IPA width of the Realm which was stored in
  the GUID HOB gArmCcaIpaWidthGuid.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>