fluent demo v1 not following app theme set by user

[Anubhvv]

Problem

V1 Activities in fluent demo app were not respecting Dark theme set by user.

Root cause

Fluent theme composable isn't used by v1 (xml based)

Fix

Using AppDelegate.setDefaultNightMode so night mode can be communicated to the v1 components.

Validations

Fluent demo app v1 themes.webm

Screenshots

Before	After
Screenshot or description before this change	Screenshot or description with this change

Pull request checklist

This PR has considered:

• [ ] Light and Dark appearances
• [ ] Automated Tests
• [ ] Documentation and demo app examples
• [ ] VoiceOver and Keyboard Accessibility
• [ ] Internationalization and RTL layouts
• [ ] Size classes and window sizes (notched devices, multitasking, different window sizes, etc)