When in greasepencil sculpt-/vertexpaint mode and using selection
masking, picking points wasnt working correctly.
So regular gpencil.select (without modifier keys) was not enabled for the
keymap. This only really makes sense for RCS (right click select) atm
(and not using RC fallback tools - which I dont think are present in
these modes anyways). With RCS, this can be supported and afaict, this
does not cause conflicts.
NOTE: prior to D16576, one could use the ALT modifier key (this
combination was actually in the keymap) -- but it should select the
entire stroke, which is handled in D16576.
Differential Revision: https://developer.blender.org/D16577
ee56c46c15