Add CV_16UC1/GRAY16_LE support to GStreamer backend for VideoWriter
* videoio(backend): add Writer_open_with_params to plugin API
This will allow arbitrary parameters to be passed to plugin backends
* videoio(gstreamer): add GRAY16_LE/CV_16UC1 writing support to GStreamer
This introduces a new property VIDEOWRITER_PROP_DEPTH, which defaults to
CV_8U, but for GStreamer can be set to CV_16U.
Also, fix another test to not fail if plugin isn't found, copying logic
from the read_write test.
* videoio(plugin): fix handling plugins with previous API level
* videoio: coding style
* fix warning
541a09b7ac