Fix "using JNI after critical" exceptions

Refactored ScopedJavaNioBuffer implementation to copy
directly to std::vector<uint8_t> instances and release
the jni critical array queries immediately after copying
into a vector. This is to avoid potential interleavings
of JNI method calls before destructor of ScopedJavaNioBuffer
is invoked. As per jni requirements no other JNI calls are
allowed after GetPrimitiveArrayCritical until a matching call
to ReleasePrimitiveArrayCritical is made.

Fixes: 271468824
Test: Added tests to MeshTest
Change-Id: Ia4afd8b8584ae43f021c79b6a341b05e80e0e205