Update documentation for ICameraProvider and CameraView

[zhitaop]

This PR updates the CameraView docs to include examples for the public methods added in CommunityToolkit/Maui#2634

This includes:

• Docs for ICameraProvider.InitializeAsync() and ICameraProvider.RefreshAvailableCameras() and the differences between them.
• Docs for how to switch the SelectedCamera for the CameraView

[zhitaop]

@microsoft-github-policy-service agree

[learn-build-service-prod]

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[learn-build-service-prod]

Learn Build status updates of commit 3643721:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/maui/views/camera-view.md	✅Succeeded	View

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