ArmVirtPkg: duplicate PlatformIntelBdsLib to PlatformBootManagerLib

ArmVirtPkg: duplicate PlatformIntelBdsLib to PlatformBootManagerLib

Create a copy of PlatformIntelBdsLib under the name
PlatformBootManagerLib, with the following initial changes:
- replace PlatformBdsLib references with PlatformBootManagerLib in
  comments,
- replace "IntelBdsPlatform" with "PlatformBm" in file names and their
  references,
- generate a new FILE_GUID.

PlatformBootManagerLib will be linked into the BDS driver from
MdeModulePkg.

This patch parallels OvmfPkg commit 305418818959.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ruiyu Ni <ruiyu.ni@Intel.com>