The spreadsheet can retrieve the float selection using the same
utilities as curves sculpt brushes. Theoretically this can work in
original, evaluated, and viewer node modes, at least when the
sculpt selection attributes are able to be propagated.
Differential Revision: https://developer.blender.org/D15393
This adds the boilerplate code that is necessary to use the tool/brush/paint
systems in the new sculpt curves mode.
Two temporary dummy tools are part of this patch. They do nothing and
only serve to test the boilerplate. When the first actual tool is added,
those dummy tools will be removed.
Differential Revision: https://developer.blender.org/D14117