Enable widget dark theme preview

When creating an application context for resources using a base context,
make sure to transfer over the base context's configurations, since this
is reset in the process. This way, when night mode is set on the base
context, the remote views are updated accordingly.

Flag: EXEMPT bug fix
Test: manually verified by toggling dark theme in Wallpaper & Style
Test: manually tested various widgets across users in dark & light theme
Test: atest CtsWidgetTestCases
Bug: 379875895
Change-Id: I83f19f5e0fdddffd19f04c6af36472a04a22b1c8