MdeModulePkg/BdsDxe: Avoid overwriting PlatformRecovery####
MdeModulePkg/BdsDxe: Avoid overwriting PlatformRecovery####

Current implementation always creates PlatformRecovery0000
pointing to \EFI\BOOT\BOOT$(ARCH).efi but it may overwrite
PlatformRecovery#### created before (maybe by a DXE driver).

The patch only uses the smallest unused option number for
the \EFI\BOOT\BOOT$(ARCH).efi PlatformRecovery#### to avoid
overwriting already-created PlatformRecovery####.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <9fa3a6894a36bca79e6a72ad65af5a5702efecd1@intel.com>
Reviewed-by: Jie Lin <e3cc085e5a907fe2f253f363cacf396d5299f3ec@intel.com>
Reviewed-by: Sunny Wang <74be04b34988dab727259a50c8e026e88682f7c8@hpe.com>

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