Improve status bar icons readability on high res ldpi displays

The first step was already done in ag/34235774, by scaling up most of
the status bar dimen resources.

In tha CL we forgot to also scale up "status_bar_icon_scale_factor" by
2x.

Test: adb shell wm size 1080x1920 && adb shell wm density 90
      adb shell 'stop;start'
Bug: 413620149
Bug: 420905041
Flag: EXEMPT only flaggable with a read-only flag
Change-Id: I45ff6e278252a3866c590d96a9dd18e9cef4c8d1