Fix connect camera cancellation

[zhitaop]

Description of Change

This PR improves CameraViewHandler lifecycle by making camera connection cancellable, preventing failures when the handler is disconnected or disposed while ConnectCamera() is still running.

Changes:

• Added cancellationTokenSource to track and cancel camera connection.
• Updated ConnectHandler() to:
  • cancel and dispose any previous token source
  • create a fresh token source for the new connection
  • safely ignore OperationCanceledException when cancellation was triggered by the handler itself
  • call DisconnectHandler() if camera connection fails for any other reason
• Updated Dispose() to cancel the active token source. This ensures ongoing camera connection is cancelled if handler is disconnected

Linked Issues

• Fixes [BUG] CameraView crashes if exited too quickly on Windows #3171

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls

Additional information

[Copilot]

Pull request overview

This PR aims to prevent Windows crashes when navigating away from CameraView while the camera connection is still in progress, by making ConnectCamera() cancellable and guarding against double-dispose.

Changes:

• Added a handler-level CancellationTokenSource to cancel in-flight camera connection work.
• Added an isDisposed guard to prevent repeated disposal.
• Updated ConnectHandler() to cancel any prior connection attempt and ignore self-triggered cancellation.

[pictos]

we don't throw here

[zhitaop]

Removed the throw statement

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

[Copilot]

ConnectHandler catches all exceptions and unconditionally calls DisconnectHandler(platformView). If the handler is already disconnecting/disposing, DisconnectHandler can throw (e.g., CameraManager field already set to null and the property throws), which defeats the goal of preventing crashes. Consider guarding this path (e.g., if cancellation was requested / handler is disposed / cameraManager is null, just return), and log the exception (Trace) for non-cancellation failures before disconnecting.