Move models json list into subdirectory.

We found that some devices add arbitrary
json files to the assets root. Moving models
list to seperate subdirectory to mitigate.

Bug: 109862575
Test: adb shell am instrument -w \
      com.example.android.nn.benchmark/android.support.test.runner.AndroidJUnitRunner

Change-Id: I91e0490fa09cfc26c3f3636189f2a9120c4877ad
Merged-In: I91e0490fa09cfc26c3f3636189f2a9120c4877ad
(cherry picked from commit 2ad4186d8b4b1ba9e8787e0a46f737b91f4b69e7)
1 file changed