Switch to open sourced fbjni (#30175)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30175
fbjni was opensourced and java part is published as 'com.facebook.fbjni:fbjni-java-only:0.0.3'
switching to it.
We still need submodule fbjni inside the repo (which is already pointing to https://github.com/facebookincubator/fbjni) for so linking.
**Packaging changes**:
before that `libfbjni.so` came from pytorch_android_fbjni dependency, as we also linked fbjni in `pytorch_android/CMakeLists.txt` - it was built in pytorch_android, but excluded for publishing. As we had 2 libfbjni.so there was a hack to exclude it for publishing and resolve duplication locally.
```
if (rootProject.isPublishing()) {
exclude '**/libfbjni.so'
} else {
pickFirst '**/libfbjni.so'
}
```
After this change fbjni.so will be packaged inside pytorch_android.aar artefact and we do not need this gradle logic.
I will update README in separate PR after landing previous PR to readme(https://github.com/pytorch/pytorch/pull/30128) to avoid conflicts
Test Plan: Imported from OSS
Differential Revision: D18982235
Pulled By: IvanKobzarev
fbshipit-source-id: 5097df2557858e623fa480625819a24a7e8ad840
