1bfa52b57c
Internationalize the default Action layer name. Instead of `"Layer"`,
use `DATA_("Layer")`. This is the same for other defaults in Blender.
When upgrading a legacy Action to a slotted Action, it also gets a layer
and a keyframe strip on that layer. Those are not shown in the user
interface yet, but will in the future.
Pull Request: https://projects.blender.org/blender/blender/pulls/133009