Accessibility: Flyout Automatically Reads All Elements on Open

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### Describe the bug

Transfer of issue https://github.com/microsoft/react-native-gallery/issues/524 to mirror internal bug logged.

When the Flyout menu is opened in screen reader mode (e.g., Windows Narrator), the screen reader automatically reads out all accessible elements within the Flyout without waiting for user interaction. This behavior can overwhelm users and prevent them from navigating through the menu items at their own pace.

### Steps to reproduce the bug

- Enable a screen reader, such as Windows Narrator.
- Open the Flyout menu.
- Observe that the screen reader automatically starts reading all accessible elements in the Flyout sequentially.
- Note that users cannot interrupt the reading to focus on a specific item or interact with the menu at their own pace.

### Expected behavior

- The screen reader should announce the Flyout as a modal dialog or menu when it opens.
- Only the first actionable element (e.g., the first menu item or header) should be read out automatically.
- Users should have control over the navigation and reading of other elements using keyboard or screen reader gestures.

### Screenshots

_No response_

### NuGet package version

None

### Windows version

_No response_

### Additional context

_No response_

Start by reproducing the Flyout behavior with Windows Narrator and trace the Flyout's accessibility and focus handling; no source file or test is identified in the issue. Done means the Flyout is announced appropriately, only the first actionable element is read automatically, and users retain control of subsequent navigation.

Written by the indexing model from the issue text.