[eslint] make CI lint tests, utils, resolvers, ...etc

[golopot]

First steps for fixing #1413.

[golopot]

See also #1413 (comment) :

There is a technical problem: Since we don't want to lint tests/files, an .eslintignore file needs to be added. But doing that alters the behavior of unit tests for no-unused-modules, the rule will consider tests/files/**/* to be ignored, hence failing the tests.

[coveralls]

Coverage decreased (-1.5%) to 96.408% when pulling c3cad51 on golopot:eslint into 2e047e6 on benmosher:master.

[golopot]

The current approach has the disadvantage that contributors 1. cannot run eslint ., but have to run eslint . --ignore-path .eslintignore-real. 2. will need to disable editors' eslint when working on tests/files/**.

I found another approach: add the file tests/files/.eslintrc, which disables all rules by rules: { "some-rule": 0, ... }. This approach do not suffer from the aforementioned problems.

I am going to force push with the later approach.

[ljharb]

I think the latter approach you suggest sounds better.

[ljharb]

We shouldn't be autofixing warnings; looks like the second commit is only doing that.

I'll rebase and clean it up a bit, thanks! <3