libandroid_net_lowpan: Reintroduce new unit tests for data classes

This change introduces new unit tests which confirm that various data
classes are being property marshalled between their Java and C++
implementations.

This was originally added to platform/frameworks/base via change id
I41d590b1e77dc41873c4b9e9bf1b7f1bf859f74e, but that change was
reverted (via ag/2553741) due the failure of build 4190632 on the
branch `git_wear-master`. Moving these specific tests into this
repository avoids this failure case.

This change is dependent on the following change id:

    I70fe6be8d71424e11a537daaa69c3f6cfae8e49d

Bug: b/63707448 b/63708348
Change-Id: I41d590b1e77dc41873c4b9e9bf1b7f1bf859f74e
Test: These tests both compile and pass
21 files changed