feat(Split): add colorScheme

[sgaczol]

Description

Adds support for colorScheme prop for SplitHost. Color scheme will be propagated down the hierarchy.

Closes https://github.com/issues/assigned?issue=software-mansion%7Creact-native-screens-labs%7C1026

Changes

• add colorScheme prop toSplitHost
• handle colorScheme on iOS side
• add test-split-color-scheme

After - visual documentation

SplitHostColorScheme.mov

Note: SettingsPicker does not update on SplitHost colorScheme updates because ThemeProvider is not used in this test. This is due to ThemeProvider not handling theme='undefined' properly, which would be necessary for the inherit case.

Test plan

Run test-split-color-scheme.tsx

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes

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