Cut dependency to libmedia_jni.so

This is a part of job to cut dependency from libmediandk
to libandroid_runtime. As a LL-NDK, libmediandk desn't have
to depend on libandroid_runtime.

depependcy:
* libmediandk -> libmedia_jni -> libandroid_runtime.

Libmediandk calls three functions defined in libmedia_jni.
However those three functions are independent from libandroid_runtime.
After extracting those utility functions into a new library
(libmedia_jni_utils), libmediandk now depends on it instead of
libmedia_jni.

Bug: 124268753
Test: m -j
Change-Id: If283fefca5cf4e282d1c29876b78037bc9df7625
Merged-In: If283fefca5cf4e282d1c29876b78037bc9df7625