ShellPkg/UefiShellLib: rebase ShellOpenFileByDevicePath() to UefiLib API

ShellPkg/UefiShellLib: rebase ShellOpenFileByDevicePath() to UefiLib API

Replace the "old shell method" implementation in
ShellOpenFileByDevicePath() with EfiOpenFileByDevicePath() from UefiLib,
correcting the following issues:

- code duplication between this module and other modules,
- local variable name "EfiSimpleFileSystemProtocol" starting with "Efi"
  prefix,
- bogus "FileHandle = NULL" assignments,
- leaking "Handle1" when the device path type/subtype check or the
  realignment-motivated AllocateCopyPool() fails in the loop.

Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1008
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>