Supporting selection operators and overlays in sculpt mode is necessary
to support masking operations.
This enables selection drawing in the overlay in sculpt mode,
and ensures all the necessary operators (pick, lasso, circle, box)
handle the differences in modes correctly.
The selection code so far was expecting object mode, so the `vc->obedit`
object was used without further checks. Now the selection code can be
called outside of edit mode, in which case the `vc->obact` object must
be used instead. Similarly edit mode and sculpt mode have separate
`selectmode` flags, so the correct mode property must be used from the
tool settings depending on the object mode. These changes require some
refactoring of unrelated selection code.
Pull Request: https://projects.blender.org/blender/blender/pulls/128040
23cd299ba7