ShellPkg: acpiview: Add -r parameter for table requirements validation

ShellPkg: acpiview: Add -r parameter for table requirements validation

Define a new command line parameter '-r' to enable checking if all
mandatory ACPI tables listed in a specification are present.

The -r parameter takes an integer value to specify which specification
the validation should be performed against.

The parameter is used to set two Acpiview variables. An interface to
access these variables is implemented in this patch.

The new functionality is aimed at Arm-based platforms, however,
there are no restriction on extending it to other architectures.
For the 32-bit and 64-bit Arm architectures, the possible values for
the -r parameter are:
  0: Arm Server Base Boot Requirements 1.0, March 2016
  1: Arm Server Base Boot Requirements 1.1, May 2018
  2: Arm Server Base Boot Requirements 1.2, September 2019

Signed-off-by: Krzysztof Koch <krzysztof.koch@arm.com>
Reviewed-by: Sami Mujawar <Sami.Mujawar@arm.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>