Blender Git Loki

Fix T86809: Action Editor header not display the right action in certain scenarios

If a new action is created (e.g. by inserting keyframes), the header was
not garuanteed to display the right action.
Notifiers were fine here, redraw took place, the editors action was just
not set soon enough for the drawing.

Now make sure this is set correctly by ensuring the animation context is
right (same as the other editor regions do before drawing).

Maniphest Tasks: T86809

Differential Revision: https://developer.blender.org/D10796