dvbsuboverlay: Dynamic resolution update support for dvbsuboverlay component

Brief: The dvbsuboverlay plugins won't adapt to the incoming resolution change for rendering subtitles.

Scenario description: When a user is fetching MpegTS (H.264+AAC+dvb-subtitle) stream from camera feed over UDP and rendering the subtitles onto video frame using dvbsuboverlay plugin. When the input camera feed changes dynamically, all other components are renegotiating and adjusting to the new resolution, but dvbsuboverlay is still holding on to dvbs co-ordinates calculated w.r.t previous video resolution and subtitle rendering looks distorted after resolution change.

Solution: I have done this enhancement in gst-plugin-bad-1.14.5, currently in the process of submitting the merge request.

The described issue is OS agnostic.

Note: Camera feed can be simulated using any MpegTS file with the above-mentioned codecs.