ShellPkg/AcpiView: Refactor DumpAcpiTableToFile

ShellPkg/AcpiView: Refactor DumpAcpiTableToFile

Method is refactored into two parts. A new method is
created that dumps arbitrary buffers into a newly created
file. This method is called from core code after the core code
determined the appropriate filename to be used.

This improves the modular design.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>
Signed-off-by: Tomas Pilar <tomas.pilar@arm.com>