The "Hide Collection" operators assigned to the number keys in edit mode
trigger a redraw of the outliner, but as an optimization, they do *not*
trigger a rebuild of the tree.
This optimization is valid because unlike the collection exclude toggle,
the heirarchy is not affected by collection visibility. However, it means
that currently you must trigger a rebuild to get the correct "grayed out"
status after using the operator.
Rather than trigger a rebuild in this case to solve the bug, this patch
moves the decision for whether to gray out the text of a tree element
to the draw step rather than the build step. This means that any change
to the corresponding properties doesn't require a full tree rebuild.
Note that changing the "hide_viewport" property from the outliner still
causes a tree rebuild. I think that's because of the checks in
`outliner_collection_set_flag_recursive_fn`.
That could be optimized in the future.
Differential Revision: https://developer.blender.org/D10240
34580748dc