Part of #91973
Moving the snapping code for the
* Graph Editor
* Action Editor
* and NLA editor
into the common system that lives on the scene.
This includes the Magnet icon for turning
snapping on and off.
The old settings translate to the new in the following way:
* `Frame Step` -> `Frame`
* `Second Step` -> `Second`
* `Nearest Frame` -> `Frame` + `Absolute Time Snap`
* `Nearest Second` -> `Second` + `Absolute Time Snap`
* `Nearest Marker` -> `Nearest Marker`
Since this moves the location of the snapping settings
from the editor to the scene, it changes the behavior.
Previously each editor could have different snapping
settings, where now they are all synced.
Pull Request: https://projects.blender.org/blender/blender/pulls/109015
11fe57cab8