ArmPkg/ArmTrngLib: Add Arm TRNG library

ArmPkg/ArmTrngLib: Add Arm TRNG library

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

The Arm True Random Number Generator Firmware, Interface 1.0,
Platform Design Document
(https://developer.arm.com/documentation/den0098/latest/)
defines an interface between an Operating System (OS) executing
at EL1 and Firmware (FW) exposing a conditioned entropy source
that is provided by a TRNG back end.

The conditioned entropy, that is provided by the Arm TRNG interface,
is commonly used to seed deterministic random number generators.

This patch adds an ArmTrngLib library that implements the Arm TRNG
interface.

Acked-by: Leif Lindholm <quic_llindhol@quicinc.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>