vapostproc: Disable cropping in pass-through mode.

Originally, if a buffer arrives with crop meta but downstream doesn't handle crop allocation meta, vapostproc tried to reconfigure itself to non pass-through mode automatically. Sadly, this behavior was based on the wrong assumption that propose_allocation() vmethod would bring downstream allocation query, but it is not.

Now, if vapostproc is in pass-through mode, the cropping is passed to downstream. Pass-through mode can be disabled via a parameter.

Given than no source pad reconfiguration is used now, gst_va_vpp_update_passthrough() doesn't have the reconf parameter anymore.

This MR goes above !2442 (merged)