Add soong flag to use speed-profile in SystemUI

This will allow us to use baseline profiles in dexpreopt for SystemUI,
if the flag is set to TRUE.

Ignore-AOSP-First: in topic with internal-first/internal-only projects

Bug: b/271887637
Test: Built locally and flashed on device
Change-Id: I85cd0e3fac5174c4b7684867fc042599a8b9486e