Fix PHP 7 parse error in the Escaper stub

[michielgerritsen]

Fixes #358. The Escaper stub added in 0.43.0 declares escapeHtml() with a native union type, and MockAutoloader require()s the stubs into the process running PHPStan, so on PHP 7 that is a fatal parse error rather than a skipped file: every analysis touching Magento\Framework\Escaper aborts with an internal error. ?array is equivalent from PHP 7.1 on. Nothing checks src/Magento today, since phpstan.neon lists only src/bitExpert, cs-check ignores it and CI runs 8.4 exclusively, so the rest closes that gap.

Change	Why
bin/ci_php_lint, from a new lint job on 7.4, 8.1 and 8.5	real php -l at both ends of the composer constraint
phpstan-stubs.neon, as analyze-stubs	its own config because a phpVersion range on phpstan.neon at level: max reports 267 unrelated errors

Worth a look: only the 7.4 entry catches this bug, 8.1 and 8.5 guard the other direction. The composer constraint moves from ^7.2 to ^7.4 in the same PR because phpstan/phpstan ^2.0 already requires 7.4, so 7.2 and 7.3 could not install 0.43.0 in the first place.

[shochdoerfer]

Do you have an older Magento project to test this change against? I am not fully sure if we run into problems when changing the method signature when analyzing classes that inherit the "original" Magento class.

But that's probably an edge-case and something to fix by future you anyways :)

[michielgerritsen]

I have. I ran it against PHP 7.2-8.5 against the corresponding Magento versions as a test. It turns out that, since PHPStan 2.0 is required, it's not possible to install it on anything lower than 7.4. I updated the PR to reflect that in the composer.json.