Add checkstyle prebuilt jar and move checkstyle.py and related files

- This adds Checkstyle 7.4-SNAPSHOT
  Taken from internal builder:
    https://android-build.googleplex.com/builds/branch-dashboard/ub-checkstyle-master?build_id=3575892
  Built from external/checkstyle 4f80bd71c5c6647112ae74163e8548e2f44e7e98
- This moves checkstyle.py and related files from
  platform/development to this repo.

Bug: 33078621
Test: Ran checkstyle.py on some test java files.
Change-Id: I91b196fb87ad01d171bf4250ce5a2101d6890a59
15 files changed