Add key ACCESSIBILITY_FONT_SCALING_HAS_BEEN_CHANGED

We use the key to track if users change the font size in Settings and
not use the default scaled value.

Bug: 269679768
Test: atest SettingsProviderTest
Change-Id: I8854f484ddec4669aa08b3ca60590fdb198dd970
Merged-In: I6a20e2af38064be2b03e2cdda530964989a2d0b0
5 files changed