Add ATrace in critical points for unfolding

Those traces will help in understanding how the time is spent during the screen unfold.
We used Debug.startMethodTracing() to identify the culprits: methods in this cl were the ones requiring more time. By adding those traces, we will be able to see them in perfetto recordings.

Bug: 197515205
Test: Manual
Change-Id: Id96e313b1e6a328335d0fc8a460452766fea7996