[34/n] Satisfy motion requirements for reachability

Letterbox Reachability animation need to use an
EMPHASIZED interpolator and a duration of 500ms.

Flag: com.android.window.flags.app_compat_refactoring
Bug: 389629565
Test: Manual

Change-Id: I53116f3284bbd3d640c3a72ef4ed45779d5529e7