Add chromium_test_compat_main function

[theonlychant]

Implement main function for Chromium test compatibility

[github-actions]

👋 Thanks for your contribution! Your PR has been imported to Gerrit.
Please visit https://dawn-review.googlesource.com/c/dawn/+/301936 to see it and CC yourself on the change.
After iterating on feedback, please comment on the Gerrit review to notify reviewers.
All reviews are handled within Gerrit, any comments on the GitHub PR may be missed.
You can continue to upload commits to this PR, and they will be automatically imported
into Gerrit.

[kainino0x]

Hi, please explain the purpose of this change. I don't know why it's needed.

[theonlychant]

Well it was a test but this change adds a Chromium-compatible test entry point. It just allows the Chromium test harness to override execution when needed, while still falling back to normal GoogleTest execution otherwise. This ensures tests run correctly both inside Chromium and in standalone environments. I don't think it is necessary though

[kainino0x]

Does something in Chromium automatically pick up this file path or does it require additional build file changes (that aren't included here) to use it? I don't want to add a file that's unused or appears to be unused.

[theonlychant]

oh yea you're right I forgot nothing in Chromium automatically picks up this file path. It would require corresponding BUILD.gn changes to be compiled and used I won't add this in the build.gn as I don't think it is necessary right now sorry for the PR