selector: Make :not() selectors not radical

selector: Make :not() selectors not radical

:not() selectors cannot be radical because the bloomfilter only knows if
a value is set in any of the nodes, but cannot determine the opposite
(if a value is not set in at least one node), but that would be required
for:not() selectors.
However, this is very unlikely to happen in the real world, so it's not
worth optimizing.

Unfortunately, change tracking could know this, so by excluding the
:not() selectors from radical changes, the change tracking will now pick
them up. If that turns out to be a performance problem, we need to add a
special category for radical not filters, so change tracking and bloom
filters can deal with them.

The testcase demonstrating the problem in widget-factory has been
extrated and added.