Use black navigation bar in black AMOLED theme

[Br1ght0ne]

AniTrend Pull Request

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Description

This changes the navbar of the black theme to match the theme, so it's better on AMOLED devices.
Supported on API v21+, so added overrides in values-v21.

Motivation and Context

Black theme uses a white navbar.

How Has This Been Tested?

Tested on API 17, API 21, API 32 emulators, on physical API 31 device.

Screenshots (if appropriate):

Before:

After:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

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[wax911]

Thanks for the PR @Br1ght0ne ❤️