Fixed illuminator state/control on dual illuminator camera (IL series)

[Trexano99]

✨ Fix: Dynamic illuminator indexing for Dahua dual smart light cameras (IL Series)

🚨 The Problem

On modern Dahua dual smart light cameras (IL series), the illuminator state and functionality were bugged. Previously, the white light was implicitly assumed to be at index 0. While this works for single-illuminator cameras, on dual-illuminator models, index 0 is assigned to the Infrared (IR) light, which breaks white light controls.

🛠️ The Solution

• Introduced get_illuminator_index: A new function to dynamically identify the correct light index regardless of the camera's hardware layout, cleanly preserving legacy behavior.
• Refactored async_set_lighting_v2: Parameterized the index within the function call, ensuring the dynamically identified light index is resolved before execution.

✅ Impact

• 💡 Successfully restores turn on/off and brightness controls for the white light on IL series cameras.
• 🛡️ Ensures strict backward compatibility for single-illuminator models.

📝 Documentation & Usage Note

To control the illuminator via the Home Assistant entity, the camera's illuminator mode must be set to manual.
(Tip: Setting the night profile to "manual illuminator" allows for consistent manual control directly from the HA entity).