Support datasets and top-k evaluation in mlts

Adds support for:
- Datasets with an input directory and ground-truth labels
- Reading inputs from jpeg instead of float/quant files
- Top-k evaluation of classification
- Creating tflite inputs as they are needed
- Inception image preprocessing

Test: adb shell 'am instrument -w -e class com.example.android.nn.benchmark.NNTest#testNNAPIAllData[mobilenet_float_topk] com.example.android.nn.benchmark/android.support.test.runner.AndroidJUnitRunner'
Bug: 112572024
Bug: 111975862
Change-Id: I3dccf333aede4cfcbe12ba0d533f9cf5bf7d2c78
Merged-In: I3dccf333aede4cfcbe12ba0d533f9cf5bf7d2c78
(cherry picked from commit 629c4c2268f0a4022ad5f0a61dcea5806ee54c6a)
17 files changed