fix: Close HardwareBuffer Java ref

[mrousavy]

Previously, we did not close the HardwareBuffer from Java/Kotlin.

We only passed it to C++ (NativeBufferHelper or Nitro's ArrayBuffer) which internally managed it's ref via AHardwareBuffer_acquire(..) and AHardwareBuffer_release(..) - but the Java HardwareBuffer was never closed.
I thought close() force deletes the underlying native buffer memory, but apparently my understanding is wrong - it simply releases the Java reference to the native buffer memory (kinda like doing a AHardwareBuffer_release(..) call).

Also I thought I'd be closing memory CameraX/ImageReader still needs (eg I thought it was pooled HardwareBuffer objects), but it seems like image.hardwareBuffer isn't a cached property: it was calling Image.getHardwareBuffer(), which created a new HardwareBuffer on each call - so we are apparently not closing any pooled HardwareBuffer objects but instead just a ref-counted Java handle. Seemed fine to close.

So not calling close() on our HardwareBuffer (which we often got from Image.getHardwareBuffer()) actually caused issues - it only fully released it after the Java GC deleted the HardwareBuffer Java object.

I wouldn't call it a leak since it did delete them, but it deleted them only after GC runs, even though we could've deleted them sooner.

For example, see the change in ImageProxy+getNativeBuffer.kt - we don't need the hardwareBuffer Java reference after this method returns - we will only have it in C++. It's fine to close this reference here now, and have C++ do the ref counting from there on.

Same for ImageProxy+getPixelBuffer.kt. After Nitro's ArrayBuffer.wrap(hardwareBuffer) consumed the HardwareBuffer, we no longer need the Java reference and can actually close it.

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Summary by cubic

Close Java HardwareBuffer references immediately after handing them to native code to free memory sooner and avoid waiting for GC. This makes buffer lifetime deterministic and reduces transient memory use.

• Bug Fixes
  • getNativeBuffer: use try/finally and call hardwareBuffer.close() after creating NativeBuffer.
  • getPixelBuffer: close hardwareBuffer after ArrayBuffer.wrap(hardwareBuffer) and when checking hasPixelBuffer.
  • Native ref counting remains unchanged; only the Java handle is closed.

^{Written for commit 95f5f36. Summary will update on new commits. Review in cubic}

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