videoconvertscale: Don't claim we can support any kind of memory

videoconvertscale: Don't claim we can support any kind of memory

Since d0133a2d11566ff4c0cded7af8dfdff0046e0e8b "videoconvert: Allow
passthrough for ANY caps features" videoconvert will always claim that
it supports any kind of memory which is true in very specific case (when
it is running in passthrough mode). To get elements that autoplug
converters depending on the caps running in the pipeline (like
autovideoconvert), we need to have converters no lie about what they can
do when queried `accept_caps` or `query_caps`.

This still accepts any caps feature as before but it introduces
a restriction in the way we handle memory capsfeatures.

We keep previous behaviour in videoconvert and videoscale.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/898>