We can avoid the rather expensive outliner tree rebuilds and only redraw
if nothing but the selection or active item changes. This should give a
bit of speedup for heavy scenes.
For this to work I had to correct a few notifiers, some were only
sending selection/active change notifiers that actually did things like
adding objects. I also added a more precise notifier type for when the
active collection changes. At the notifier subtype/action level we're
not even close to running out of bits, so this should be fine.
Also had to correct a wrong notifier check (was using `&` rather than
`==`).
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