SceneTracker::FlushDirty ensures that we record Prefab instance overrides for dirty objects.

A user can change a property and mark the object dirty and expect that overides are automatically being recorded.

This logic is causing problems for Timeline which are often animating 1000s of Transforms while also marking the transforms dirty.

It has shown that this costs around 1000 ms when previewing animations for the Enemies demo. 

See detailed discussion in this slack thread: https://unity.slack.com/archives/C06TQFQ7P/p1675800164129839