Cleanup linter check
Cleanup linter check

- Remove duplicate handling of subprocesses
- Remove indirection of js_lint (we can simply name it main)

These cleanups allow us to later optimize the linting step by only
linting changed files.

R=8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org

Change-Id: Ifb8fdb3a25ea04a4879d434d85ff44aa17dae012
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2088091
Commit-Queue: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>
Reviewed-by: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>

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