Port c2 e2e encoder tests

The new files are more or less directly copied from the cros tree. The
changes are fixing import paths, hooking up to the jni instead of main,
removing some code targeting N, and reformatting.

Unlike the decoder tests, the encoder tests do not currently benefit
from being in the Android tree. However, porting the tests prevents the
need to duplicate the helper code between Android and cros, and it
unifies how the two sets of tests are built and run.

Test: run encoder tests based on README.md
Bug: 144681449

Change-Id: I7600cae82693ff6994770954243ec128acdada36
(cherry picked from commit c63a8aac405092c2928408b721d18607503bca21)