Blender Git Loki

Fix [#20663] Mouse cursor icon changes back to default in edit mode

Seemed simple but actually turned out to be quite complex.

ND_MODE notifier was being misused, changed to ND_TOOLSETTINGS

Note: Although the fix itself doesn't involve this much, debugging uncovered
that listeners can't rely on notifier->swinid to be correct, since notifiers can
now be added from RNA without a region context.