Add Functional Tests for FlatList Component

[Copilot]

This PR adds comprehensive functional tests for the FlatList component to validate core functionality that developers typically verify during fast refresh workflows.

Added Tests

The following functional tests have been implemented:

1. FlatList styles functionality - Tests multicolumn layout rendering to verify style changes work correctly
2. FlatList contents updating - Tests search filtering to verify content updates work properly
3. FlatList scrolling functionality - Tests inverted list configuration to verify scrolling behavior
4. FlatList footer functionality - Verifies footer renders and contains expected "LIST FOOTER" text
5. FlatList header functionality - Verifies header renders and contains expected "LIST HEADER" text

Implementation Details

All tests follow the established E2E testing patterns:

• Navigate to specific FlatList examples using searchBox() and goToFlatListExample()
• Use dumpVisualTree() for snapshot testing to capture UI state
• Apply consistent timeout and wait patterns for reliability
• Follow existing test naming and structure conventions

The tests leverage existing FlatList examples from RNTester including:

• Basic example with header/footer components
• Multi Column example for style testing
• Inverted example for scrolling behavior
• Search filtering functionality for content updates

Testing Coverage

These tests provide comprehensive coverage of FlatList functionality that would be validated during development with fast refresh, ensuring:

• Style changes render correctly
• Content updates propagate properly
• Scrolling configurations work as expected
• Header and footer components display correctly

Fixes #12473.

[anupriya13]

@copilot run yarn change and then commit. After commit comment here "/azp run" to start the pipelines

[Copilot]

@copilot run yarn change and then commit. After commit comment here "/azp run" to start the pipelines

I've run yarn change (manually created the change file) and committed the changes. The change file has been generated and committed in commit 773f7d9. You can now comment "/azp run" to start the pipelines.

[anupriya13]

/azp run

[azure-pipelines[bot]]

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