ETK: make PHP linting PHP 8 compatible

[simison]

Proposed Changes

• Add config to phpcs.xml suppressing PHP run-time notices (E_DEPRECATED) which allows running the linter with PHP8.

The issue is fixed in WordPress-Coding-Standards develop branch but hasn't been released yet. Their latest release 2.3.0 is from May 2020. The slution was suggested in a comment WordPress/WordPress-Coding-Standards#2035 (comment)

Testing Instructions

• Open apps/editing-toolkit
• In PHP8, run yarn lint:php

Before the change, you see errors like:

FILE: editing-toolkit/editing-toolkit-plugin/newspack-blocks/synced-newspack-blocks/class-newspack-blocks-api.php
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 1 | ERROR | An error occurred during processing; checking has been aborted. The error message was: trim(): Passing null to parameter #1 ($string) of type string is deprecated in
   |       | /wp-calypso/vendor/wp-coding-standards/wpcs/WordPress/Sniffs/NamingConventions/PrefixAllGlobalsSniff.php on line 280
   |       | (Internal.Exception)
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

After the change you see only regular linting errors/warnings.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?

Related to #

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-51463

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-51463&env=jetpack

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[tyxla]

Noting this will disable all deprecated syntax and not just the syntax that was deprecated in PHP 8. Is that intentional? If yes, then we might want to be explicit about it in the comment.

[simison]

Open to ideas how to limit this just to specific errors or even just when running in PHP, but keep runtime errors for other versions, or even just for CI runs.

I'll update the comment tho!

[tyxla]

I don't think there's a better way to do it TBH. I'm fine with this temporary approach, as long as we're explicit about it in the comment.

[simison]

check the new one out, 3980d3a

[tyxla]

Looks good, thank you 🙌

[tyxla]

Good to go once comment is updated 🚀