ArmVirtPkg/PlatformBootManagerLib: add EnableQuietBoot & DisableQuietBoot

UefiBootManagerLib does not provide these functions, we have to implement
them. (EnableQuietBoot() puts up the nice TianoCore logo.)

OvmfPkg commits 817fb3ac2a78 and 8e8fd3037788 have extracted these
functions already,
- from "IntelFrameworkModulePkg/Library/GenericBdsLib/BdsConsole.c"
- to "OvmfPkg/Library/PlatformBootManagerLib/QuietBoot.c".

Copy the latter file, with minimal changes.

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>