OvmfPkg/PciHostBridgeLibScan: create from PciHostBridgeLib
    
    Create an almost verbatim copy of the
    "OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf" library instance.
    
    The new PciHostBridgeLibScan instance will ultimately duplicate a
    negligible amount of code from the original, and will be used by the Bhyve
    and OvmfXen platforms.
    
    List the new driver in "Maintainers.txt", in the "OvmfPkg: bhyve-related
    modules" and "OvmfPkg: Xen-related modules" sections.
    
    This patch should be reviewed with "git show --find-copies-harder".
    
    Cc: Anthony Perard <anthony.perard@citrix.com>
    Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Julien Grall <julien@xen.org>
    Cc: Peter Grehan <grehan@freebsd.org>
    Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
    Cc: Rebecca Cran <rebecca@bsdio.com>
    Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>