ximagesrc: Gather and coalesce all damaged areas before retrieving.
ximagesrc: Gather and coalesce all damaged areas before retrieving.

These days the xserver seems to give us the same damage regions
over and over for entire windows, and we retrieve them multiple
times, which gives time for more damage to appear. Instead, just
quickly gather all damaged areas into a region list and copy
out once.

stfl/gst-plugins-good,pexip/gst-plugins-good,StreamUtils/gst-plugins-good,GrokImageCompression/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good,GrokImageCompression/gst-plugins-good,pexip/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,StreamUtils/gst-plugins-good,hizukiayaka/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,hizukiayaka/gst-plugins-good,Kurento/gst-plugins-good,stfl/gst-plugins-good,GrokImageCompression/gst-plugins-good,Kurento/gst-plugins-good,hizukiayaka/gst-plugins-good,stfl/gst-plugins-good,stfl/gst-plugins-good,pexip/gst-plugins-good,pexip/gst-plugins-good,Kurento/gst-plugins-good,pexip/gst-plugins-good,Kurento/gst-plugins-good,GStreamer/gst-plugins-good,hizukiayaka/gst-plugins-good,Kurento/gst-plugins-good