Buck test targets robolectric,instrumentattion
Summary:
Buck targets for robolectric and instrumentation tests for pytorch android:
```
buck test fbsource//fbandroid/mode/server //xplat/caffe2/android:test_host
```
```
buck test //xplat/caffe2/android:test_instrumentation
```
For both:
```
buck test fbsource//fbandroid/mode/server //xplat/caffe2/android:pytorch
```
Models in assets:
`pt_android_test_asset` - creates buck target that can be included in both robolectric and instrumentation tests that contains asset created from provided torchscript sources as separate file, using the latest binaries of libtorch.
`pt_gen_test_asset_bin` does that tacing, usage format
```
generate_test_asset input_file.jit output_file.py
```
Example of test-host setup for users of pytorch android:
robolectric tests:
```
load("fbsource//xplat/caffe2:pt_defs.bzl", "pt_android_test_asset", "pt_predictor_binary", "PT_ANDRIOID_TEST_HOST_JNI_DEPS")
pt_android_test_asset(
name = "test_asset",
src = "test_asset.jit",
asset_name = "test_asset.pt",
)
robolectric3_test(
name = "example_test_host",
srcs = [...],
jni_deps = PT_ANDRIOID_TEST_HOST_JNI_DEPS,
deps = [
":pytorch_common",
":test_asset",
"//fbandroid/java/com/facebook/soloader/annotation:annotation",
"//fbandroid/java/com/facebook/testing/robolectric/v3:v3",
"//fbandroid/libraries/soloader/java/com/facebook/soloader:soloader",
"//fbandroid/third-party/java/robolectric3/robolectric:robolectric",
],
)
```
COMMON_LINKER_FLAGS = ["-Wl,--no-as-needed"] can not be applied on MacOs
Test Plan:
```
[twsvcscm@od0187.atn1 /data/sandcastle/boxes/fbsource (b416b20a)]$ buck test fbsource//fbandroid/mode/server //xplat/caffe2/android:pytorch
Parsing buck files: finished in 7.2 sec
Creating action graph: finished in 0.7 sec
Building: finished in 11.9 sec (100%) 791/791 jobs, 0 updated
Total time: 19.9 sec
Testing: finished in 11.0 sec (30 PASS/0 FAIL)
RESULTS FOR //xplat/caffe2/android:test_host //xplat/caffe2/android:test_instrumentation
PASS 159ms 15 Passed 0 Skipped 0 Failed org.pytorch.PytorchHostTests
PASS 152ms 15 Passed 0 Skipped 0 Failed org.pytorch.PytorchInstrumentedTests (localhost:31930)
TESTS PASSED
```
OSS changes test:
```
gradle -p android pytorch_android:cAT passes
```
Reviewed By: dreiss
Differential Revision: D18799005
fbshipit-source-id: 881609826a837efebc8526aee40355c5a62947d0
