This commit moves the namespaced functions inside `paint_intern.hh` into their own header files, specifically: * `blender::ed::sculpt_paint::hide` to `paint_hide.hh` * `blender::ed::sculpt_paint::mask` to `paint_mask.hh` This commit also moves methods defined in `sculpt_hide.hh` into their own file (`sculpt_hide.cc`) out from `sculpt.cc` and `paint_hide.cc` Pull Request: https://projects.blender.org/blender/blender/pulls/126668