feat(cameras): add ZED camera extension and RGB viewer CLIs

[juelg]

• Add a new rcs_zed extension with SDK-backed camera discovery, streaming, and frame handling
• Introduce rgb-view CLI commands for rcs_zed, rcs_realsense, and rcs_usb_cam
• Wire ZED color, depth, timestamps, intrinsics, and optional IMU data into the shared RCS camera interface
• Add packaging/setup files for the ZED extension so it can be built and run consistently with other camera backends
• Cover ZED enumeration, multi-camera open behavior, depth scaling, and IMU handling with tests
• Fix RealSense calibration retry logic and correct AprilTag grayscale conversion to use RGB input