Dexopt the launcher(s) after a Mainline update.

For consistency with commit 296bff69ead68553800eff41fa30d49654b32d78 in
art/.

Test: adb install com.google.android.art.apex
      adb reboot
  and check logcat that com.android.systemui and
  com.google.android.apps.nexuslauncher get passed down to
  PackageDexOptimizer.dexOptPath with "verify" and "speed-profile",
  respectively.
Bug: 269140736
Bug: 251903639
Change-Id: I3b0294fcd93c7d61789e5caa1141cad8070d0838