Let desktop-first policy fully resolve the windowing mode

This CL lets desktop-first policy fully resolve the windowing mode.
Currently it only overrides the windowing mode to be FREEFORM but the
spec requires more granular control (e.g., ActivityOptions respect,
fullscreen relaunch).

Flag: com.android.window.flags.enable_desktop_first_policy_in_lpm
Bug: 427828063
Bug: 431866074
Test: DesktopModeLaunchParamsModifierTests
Change-Id: I7de7a1c15182e6d9e1d422749a12e90a0e53197d