[camera_android_camerax] Improve documentation on cameraId parameter

[camsim99]

Clarifies what cameraId is used for in each of the plugin methods.

Fixes flutter/flutter#126270.

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[camsim99]

Overriding changelof and version updates because this is just documentation updates with no direct benefit to clients.

[gemini-code-assist]

Code Review

This pull request significantly improves the documentation across various methods in android_camera_camerax.dart by explicitly clarifying the role and usage of the cameraId parameter. These changes enhance the clarity and understanding of the API for developers, making it easier to comprehend how each method interacts with specific camera instances. The updates are consistent and directly address the stated objective of the pull request.