Camera: Cleanup CameraManager

[HTRamsey]

This should fix a use after free issue
Just stop requesting messages during the RequestMessageTest rather than deleting the manager itself.
Formatting fixes

[DonLakeFlyer]

Should the prepareDelete do a camera manager stop now instead of nothing. Just to be safe?

[Copilot]

Pull Request Overview

This PR refactors the CameraManager to fix a use-after-free issue in the RequestMessageTest by implementing a stop mechanism instead of deleting the manager entirely. The changes also include code reorganization and cleanup for better maintainability.

• Replaces deleteCameraManager() with stopCameraManager() to gracefully stop camera requests during testing
• Reorganizes Camera Manager code into a dedicated section within the Vehicle class for better maintainability
• Improves code quality through consistent formatting, explicit types, and safer memory management

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/Vehicle/RequestMessageTest.cc	Updated test to use stopCameraManager() instead of deleteCameraManager() to prevent use-after-free
src/VideoManager/VideoManager.cc	Added include for MavlinkCameraControl header
src/Vehicle/Vehicle.h	Reorganized camera manager declarations into dedicated section and updated API
src/Vehicle/Vehicle.cc	Moved camera manager implementation to dedicated section and simplified lifecycle management
src/QmlControls/QmlObjectListModel.h	Added isEmpty() convenience method
src/Camera/QGCCameraManager.h	Refactored class structure with improved organization and added start/stop functionality
src/Camera/QGCCameraManager.cc	Comprehensive refactor with improved error handling, memory safety, and code organization
custom-example/src/FirmwarePlugin/CustomFirmwarePlugin.h	Removed unused CustomCameraManager forward declaration

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[HTRamsey]

@DonLakeFlyer so one question I have is the original code only removes one stale camera at a time in _checkForLostCameras, any reason not to iterate all of them? I guess it's just deferring the rest of the cleanup to 500ms later but I don't see why you wouldn't just perform the full loop.