JNI native memory leak - release array elements (#10981)

JNI native memory leak - release array elements (#10981)

Summary:
Closes https://github.com/facebook/rocksdb/issues/10980

Reproduced as per the suggestion in the ticket, and `$ jcmd <PID> VM.native_memory | grep Internal` reports that we are no longer leaking internal memory with the suggested fix.

I did the repro in `MultiGetTest.java` which I have optimized imports on. It did not seem helpful to leave the test code around as it would be onerous to build a memory leak reproducer, and regression seems a remote possibility.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10981

Reviewed By: riversand963

Differential Revision: D41498748

Pulled By: ajkr

fbshipit-source-id: 8c6dd0d608172879c8bda479c7c9c05c12d34e70