Design task: T65607
The patch adds a new flag for each animation space, allowing to hide the markers region per editor, at the same time it removes the ability to show/hide the markers' lines, that are now always drawn. It also changes markers' UI and operators accordingly.
- In anim_markers.c a new function substitutes ED_operator_animview_active in the operator polls, it also checks if the area is drawn in the editor in which the operator is called.
- In the editor flags in the dna, SHOW_MARKER_LINES is renamed in SHOW_MARKERS
- In rna_space.c a new property is set per animation space, called show_markers
- The versioning part does seem to work but I'm really not sure if I did it right
- Added a Show Markers entry in the View menu of the animation editors
- If the markers region is not active then the Marker menu gets hidden
- Driver editor: removed marker menu and don't allow to use marker operators.