Summary:
Generate Fabric C++ files along side TM spec files for RNTester. The combined .so then has both TM and Fabric files.
This commit also removed the checked-in JNI files.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D25674313
fbshipit-source-id: 8091d5a00f42849a74cab50e8d24f4010d500e5b