Update SCVH InputTransferToken when available

Use the SCVH sidechannel to update host InputTransferToken when the view
that is attached to the SCVH itself becomes attached to a window. This
will update the mapping in WMS and allow the input APIs to work as
expected. This allows callers to add a window with a SCVH instead of
waiting until the window is created. As a result of this change, we
allow SCVH to be reparented from one window to another.

This cl also relaxes the requiement of passing a host
InputTransferToken. The caller can rely on the sidechannel to pass the
correct token when the SCVH is attached to a SurfaceView.

Bug: 392965431
Test: presubmit
Flag: com.android.window.flags.update_host_input_transfer_token
Change-Id: I6cdbadfd1dfe1cd54426bfdf11de783c189fc091