Add jni_headers to libframeworks_coretests_jni

Preparation for removing implicit include paths for jni.h from soong.

Bug: 152482542
Test: m checkbuild
Change-Id: Ie6815286723cddae1765625a1455ef8847105df8
Merged-In: Ie6815286723cddae1765625a1455ef8847105df8
(cherry picked from commit 8046836b)