playbin3 : Add force-sw-decoders equivalent
It's currently difficult for applications to implement something equivalent to playbin2's "force-sw-decoders" for playbin3.
Some features are added dynamically by plugins, so filtering by feature early on isn't possible and GST_ELEMENT_FACTORY_TYPE_HARDWARE
is only available at the feature level.
The API proposed in: gst-plugins-base#758 (closed) would make it easier to disable those plugins as they become available/when they're being queried.