Apply user dark mode preference to splashscreen

[seve-andre]

What I have done and why As previously attempted here, this PR aims to align the splash screen with the user's dark mode preference. However, this solution only works for API >= 31 (see screen recordings below).

API >= 31

API-31-nia.webm

API

API-30-nia.webm

Related issues/PRs: https://github.com/android/nowinandroid/issues/633 https://github.com/android/nowinandroid/pull/646

[mlykotom]

There are conflicts now with the PR because of work that I did in the past. But, it will actually simplify your work here, because the only thing now needed is to call the setAppTheme