Update PHPStan to v2, improve code quality

[swissspidy]

Summary

Fixes #776

Relevant technical choices

• Updates PHPStan and extensions to v2
• Moves PHPStan dependencies to a new phpstan folder, because PHPStan v2 requires PHP 7.4, whereas this repo requires PHP 7.2+
• Requires swissspidy/phpstan-no-private
• Moves hooks in the PL plugin to hooks.php like in the other plugins for consistency, makes it easier to separate that code from the constant definitions in load.php

[swissspidy]

Strangely I cannot reproduce the https://github.com/WordPress/performance/actions/runs/12256447140/job/34191719008?pr=1729 error locally right now 🤔 I got it earlier but thought I had resolved it.

[westonruter]

So there is a new phpstan root directory?

[swissspidy]

Yes. Could also be renamed.

[westonruter]

We have an existing tools/phpstan directory that could be reused.

[swissspidy]

Hmm not sure I wanna mix the config directory with that one

[swissspidy]

Since we had build-cs before I could just rename it to that.

[westonruter]

• Moves PHPStan dependencies to a new phpstan folder, because PHPStan v2 requires PHP 7.4, whereas this repo requires PHP 7.2+

This is unfortunate since we previously maintained two separate composer.json files but were able to go to one, as I recall.

I wonder if we should bump the minimum PHP version to 7.4 for the entire project to facilitate maintenance and considering that core will likely bump the minimum version to 7.4 in in the middle of 2025 per Core-62622. We could still run PHPUnit on 7.2 in GHA for now if we want to.

[swissspidy]

Ah true, there was a build-cs folder before, but I can't see where it was removed at first glance.

Bumping requirements is of course the easiest route, but I thought we just recently discussed not bumping PHP version requirements unnecessarily if we can avoid it.

[swissspidy]

Strangely I cannot reproduce the WordPress/performance/actions/runs/12256447140/job/34191719008?pr=1729 error locally right now 🤔 I got it earlier but thought I had resolved it.

@westonruter is it passing for you locally?

[westonruter]

Ah true, there was a build-cs folder before, but I can't see where it was removed at first glance.

It was removed when we bumped to PHP 7.2 in #1130.