Wire-up default force-dark based off of isLightTheme

Bug: 102591313
Test: Compared settings in light & dark UI modes with
force_dark set to true. Observed that force_dark fixes
were not present when UI mode was set to dark, indicating
force_dark was appropriately globally-disabled

Change-Id: I5882829bb5871829fc8fc9911682f52a6ba5f445