This is the initial implementation of the `codegen` cli utility
for in-place java boilerplate generation
See DataClass and SampleDataClass for documentation/guide/examples.
See tools/codegen/ for implementation and tests/Codegen/ for tests.
Bug: 64221737
Test: . frameworks/base/tests/Codegen/runTest.sh
Change-Id: I75177cb770f1beabc87dbae9e77ce4b93ca08e7f