When erasing, sculpting or tinting, the previous key was not being
duplicated.
The `ed::greasepencil::ensure_active_keyframe` didn't have a good
mechanism to make this work. This adds a parameter to the
`ensure_active_keyframe` function so that the caller can decide
what should be done.
For the sculpting tools, eraser, and tint tool, this will now duplicate
the previous key, when auto-key is on.
Resolves#124082.
Pull Request: https://projects.blender.org/blender/blender/pulls/125224
fc49a5928b