Draft: videoencoder: allow merging headers rather than pushing them separately
Copied from https://gitlab.freedesktop.org//gstreamer/gst-plugins-base/-/merge_requests/1114
To respect specific bitstream alignment requirement, like found in H264/H264, allow merging repeated headers rather then pushign them seperatly.
Related to gst-plugins-bad!2178 (merged)
p.s. this is still a draft since it wasn't fully tested