Add multi-camera api example

I'm working on stereo image capture on an Android device but can't find any examples of the Android NDK multi-camera API. The only reference I found is the test code on [android official tests](https://android.googlesource.com/platform/cts/+/refs/heads/android13-release/tests/camera/libctscamera2jni/native-camera-jni.cpp). Do you have any plan to add multi-camera api ndk samples ?

Start by reviewing the Android official test reference, native-camera-jni.cpp, to understand the multi-camera NDK coverage requested. Then inspect the existing Android NDK samples to determine where such an example would belong; done would be a documented multi-camera API sample for stereo image capture.

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