Fix the order of talkback focus for ConversationLayout when expanded

Talkback can now correctly focus the collapse button before going to the action list when expanded. To know why mExpandButton is dynamically placed, check commit: 54fe9ad2

Bug: 237505828
Test: Visual, see the STEPS TO REPRODUCE section of bug 237505828, the focus order of talkback should be collapse button then actions.
Change-Id: Id0cf8730b00e0e7636a163fb5d51e37e8e0a3e84