libbluetooth_jni: Add a version_script to hide symbols

Hidding symbols let the linker discard more unused code.

This reduces the libbluetooth_jni.so size by 3.9M.

Bug: 265285999
Test: m libbluetooth_jni
Change-Id: I4dd9b681fe58335d79da39e55c7c18b7abf3a486