In Blender 4.2 in Grease Pencil draw mode it was possible to
erase strokes using box and lasso gestures.
Under the hood, these were just using the selection operators
that had special deletion handling if the object was in draw mode.
Rather than hacking this into the selection operations, this adds
two new operators:
* `grease_pencil.erase_lasso`
* `grease_pencil.erase_box`
When using one of the erase operations with auto-key, the previous
keyframe will be duplicated to the current frame (for the drawings
that are affected by the eraser).
They are mapped to the same shortcuts than the selection
operators in Blender 4.2.
* Lasso erase: `Ctrl`+`Alt`+`RMB`.
* Box erase: `B`.
This is part of #130518.
Pull Request: https://projects.blender.org/blender/blender/pulls/131504
612be514c6