This removes the legacy Grease Pencil modifiers from the code.
These should have already been inaccessible from the UI and hidden from
the user. The modifiers have been reimplemented for the new GPv3
data structure.
On top of the modifier code, some other related things have been
removed as well:
* Operators related to the legacy modifiers.
* Keymaps for the legacy modifier operators.
* Some bits of code that used modifier functions.
Some code has to be kept, because it is still used:
* The core line art code, which is used by the new line art modifier. It's
moved to `modifiers/lineart`.
* The DNA structs for the legacy modifiers. They are still needed for
conversion.
* A few kernel functions for the modifiers are kept (also for conversion).
Co-authored-by: Lukas Tönne <lukas@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/125102
0f42f277b7