SecurityPkg/RngDxe: Add Arm support of RngDxe

Bugzilla: 3668 (https://bugzilla.tianocore.org/show_bug.cgi?id=3668

)

Add RngDxe support for Arm. This implementation uses the ArmTrngLib
to support the RawAlgorithm and doens't support the RNDR instruction.

To re-use the RngGetRNG(), RngGetInfo() and FreeAvailableAlgorithms()
functions, create Arm/AArch64 files which implement the arch specific
function GetAvailableAlgorithms(). Indeed, FEAT_RNG instruction is not
supported on Arm.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Acked-by: Jiewen Yao <jiewen.yao@intel.com>