ArmVirtPkg/PlatformBootManagerLib: display boot option loading/starting

ArmVirtPkg/PlatformBootManagerLib: display boot option loading/starting

Consume PlatformBmPrintScLib, added earlier in this series. When
BdsDxe+UefiBootManagerLib report LoadImage() / StartImage() preparations
and return statuses, print the reports to the UEFI console. This allows
end-users better visibility into the boot process.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1515418
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>