OvmfPkg: QemuBootOrderLib: featurize PCI-like device path translation
    
    In preparation for adding OpenFirmware-to-UEFI translation for "MMIO-like"
    OFW device path fragments, let's turn the currently exclusive "PCI-like"
    translation into "just one" of the possible translations.
    
    - Rename TranslateOfwNodes() to TranslatePciOfwNodes(), because it is
      tightly coupled to "PCI-like" translations.
    
    - Rename REQUIRED_OFW_NODES to REQUIRED_PCI_OFW_NODES, because this macro
      is specific to TranslatePciOfwNodes().
    
    - Introduce a new wrapper function under the original TranslateOfwNodes()
      name. This function is supposed to try translations in some order until
      a specific translation returns a status different from
      RETURN_UNSUPPORTED.
    
    - Introduce a new Feature PCD that controls whether PCI translation is
      attempted at all.
    
    - The boot option "survival policy" in BootOrderComplete() must take into
      account if the user was able to select PCI-like boot options. If the
      user had no such possibility (because the Feature PCD was off for
      PCI-like translation), then we ought to keep any such unselected boot
      options.
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>