And fix all the tests as we need to wait for the project to be loaded
to check the reference count of the timeline (as we keep a ref on the
timeline in project to later emit "loaded" on idle).
The GNL API changed to go from a model where user could
enable/disable updates in the composition, which leaded to races
in many places, to a model where any positioning change in the
composition is not directly done but 'cached' and then the user
has to commit those changes so they become effective in the media
processing stack.
The new API in GES is pretty similare and is basically copy
pasting this new design.
We still need to see if in some context it would make sense to add
a mode where we would commit any changes ourself at the end of our
operation for basic use cases.
Removed APIs:
ges_timeline_enable_update
ges_timeline_is_updating
ges_track_enable_update
ges_track_is_updating
New APIs:
ges_track_commit
ges_timeline_commit
+ Fix tests (we still need a round of modernisation, making use of
assets where it makes sense)
There is no reason to use those method outside of GES, so remove them,
cleaning the API and making it easier for users.
Removed APIs:
-----------
* ges_clip_create_track_element
* ges_clip_create_track_elements
This way we let the possibility to the user to actually do it, but we avoid him to do it
without knowing it is absolutely not recommanded to.
API:
+ ges_uri_clip_asset_request_sync
