This is different from previous attempt https://codereview.chromium.org/1915463002 .

The change is completely backwards-compatible, and doesn't introduce recipe
expectation changes.

Modules can be switched to depend on infra_paths independently,
without any expectation changes either.

By moving path module's config.py to paths_config.py here, we also guarantee
that the returned results are going to be exactly the same.

Depends on https://codereview.chromium.org/1923363003 .

BUG=chromium:605919

Review-Url: https://codereview.chromium.org/1926033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@300324 0039d316-1c4b-4281-b951-d872f2087c98