Clang-Tidy: refactoring clang_tidy_warn.py

Authors: Emma Vukelj, Elaina Guan

This CL moves the warn_patterns dictionary and its dependencies into a
seperate file which the original clang_tidy_warn.py imports. This is
done for clarity and easier navigation of the original code.

BUG=None
TEST=No functionality was changed, original tests still work

Change-Id: I248ed2e62cd5192d1d5a900d988424cf24b0047a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1637609
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Emma Vukelj <emmavukelj@google.com>
2 files changed