Instead of having it all handled by the tool, this way we can
set the restriction before clips are added to the timeline,
leading to better behavior in term of video images placement
in the scene.
Without that we would have the clips positioned before setting the
restriction caps which leads to weird behavior for the end users.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-editing-services/-/merge_requests/227>
Force a string type for structure values obtained through parsing a
serialized timeline by inserting a (string) specifier after a '=',
rather than relying on gst_structure_from_string guessing the type.
As such, the functions that extract clocktimes and properties are
modified to accept string value types.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-editing-services/-/merge_requests/123>
