Depending on the outliner display mode and the outliner dirty state,
a sync may not be needed on each draw. This commit adds a check
before syncing to prevent syncing when not needed.
This changes from-outliner selection syncing to always sync the
selection state of objects. This allows selecting objects while in
edit mode for parenting or adding hooks. This also fixes a few issues
where the sync algorithm would fail when no active object existed.
Adds a toggle to the filter menu for outliner synced selection. Enabled
by default, this ensures selection is synced between objects, bones, and
sequences. An active outliner element theme color is added to indicate
which element is active.
Synced selection is controlled on the operator level. Each operator
that modifies selection for objects, bones, sequences, or outliner
elements needs to call the respective ED_outliner_select_sync_from..
function to tag outliners to be synced.
Syncing is done lazily on outliner draw.
