Switch to new PHPCSStandards/PHP_CodeSniffer package

[mindctrl]

The Squizlabs/PHP_CodeSniffer package has been deprecated. It has been forked and will be maintained under a new package at PHPCSStandards/PHP_CodeSniffer.

Reference: The Future of PHP_CodeSniffer · Issue #3932 · squizlabs/PHP_CodeSniffer

Acceptance Criteria

• Existing squizlabs package is removed and replaced with the new one.
• Existing phpcs tests continue to pass. If failures happen after upgrading, the changes needed to make it pass should happen in the same PR.

[justlevine]

@mindctrl this shouldn't be necessary: squizlabs/PHP_CodeSniffer#3932 (comment)

That said, regardless there's no need to include phpcs in this package directly unless you are intentionally pinning a specific version, as it is included upstream from vipcs