gst: Add getters for Stream and FrameBuffer

This adds getters on pad/pool/allocator so that we can retrieve the
Stream or FrameBuffer.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/gstreamer/gstlibcameraallocator.cpp

@@ -243,3 +243,11 @@ gst_libcamera_allocator_get_pool_size(GstLibcameraAllocator *self,
 
 	return pool->length;
 }
+
+FrameBuffer *
+gst_libcamera_memory_get_frame_buffer(GstMemory *mem)
+{
+	auto *frame = reinterpret_cast<FrameWrap *>(gst_mini_object_get_qdata(GST_MINI_OBJECT_CAST(mem),
+									      FrameWrap::getQuark()));
+	return frame->buffer_;
+}