Add PACKAGE.star

Adds //infra/config/global/PACKAGE.star, which is a necessary first step
for using the chromium-luci Starlark code to set up src-side builders.

Since this ends up enabling some additional linting, several no-op
changes are made to several Starlark files.

Bug: 385317083
Change-Id: I5eef4d49a0745e8bde7c214a5105589f9f318398
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/255495
Auto-Submit: Brian Sheedy <bsheedy@google.com>
Commit-Queue: Brian Sheedy <bsheedy@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@google.com>