Move JniConstants from libnativehelper to libcore

As part of refactoring NATIVE_METHOD macro is taken from
libnativehelper/jni_macros.h which does signature checking. There are
a small number of JNI method clean-ups from this.

Bug: 119840313
Test: rebase on master && atest CtsLibcoreTestCases

Change-Id: Id6af78df5d8a2458e1edc2697db5d04d99bb96db
30 files changed