ArmVirtualizationPkg: PlatformIntelBdsLib: add basic policy

ArmVirtualizationPkg: PlatformIntelBdsLib: add basic policy

In PlatformBdsPolicyBehavior() we should follow the same pattern as in
OvmfPkg's: after the consoles are connected,
- connect all drivers and devices,
- enumerate all boot options,
- enter the Intel BDS FrontPage if the user presses a key different from
  Enter.

We set the countdown to 3 seconds, similarly to the timeout that we
specify for ARM BDS.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Olivier Martin <Olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16569 6f19259b-4bc3-4df7-8a09-765794883524