Include validator code in lint and presubmit checks

[rsimha]

The code in validator is currently exempted from gulp lint and gulp presubmit. It's probably worth removing these exemptions, so that the validator code can benefit from all the new checks we've recently put in place (to the extent it makes sense to do so).

See https://github.com/ampproject/amphtml/blob/master/build-system/config.js#L125-L158

[rsimha]

/to @Gregable @honeybadgerdontcare @powdercloud

[ampprojectbot]

This issue hasn't been updated in awhile. @Gregable Do you have any updates?

[honeybadgerdontcare]

@rsimha is this covered by #18601 or do we need to do more than fixing those lint issues?

[rsimha]

Yeah, the issues are similar. #18601 was for fixing the lint errors, and this issue was for updating the rules used to lint validator/. I have no objections to combining the two into one issue.

[honeybadgerdontcare]

Ah, so this issue is "turn on linter errors" once all lint issues are fixed.

[ampprojectbot]

This issue hasn't been updated in awhile. @Gregable Do you have any updates?

[rsimha]

Per conversation with @Gregable, validator/ can rely on internal g4 lint rules. This issue is obsolete, and will be closed by #21212.