Summary:
This commit:
* Generate Fabric component Java files along side Java NativeModule specs, when `USE_FABRIC=1` is set
* Adjust the component codegen to place output files in a subdir based on package name
* Adjust existing Buck targets to filter the right nativemodule vs component java files (this avoids duplicated symbols)
* Compiles the Java output during build time on RNTester/ReactAndroid (Gradle)
Not in this commit:
* Fabric C++ files
* Removing checked-in generated component files.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D25416614
fbshipit-source-id: fd670ead2198c9b5a65812c692b7aed9f3d7cd58