Update PHPUnit GH action wp-env & wp-phpunit

[imath]

Now WordPress 5.9 has been released, we should update our PHPUnit GH action as well as @wordpress/env and wp-phpunit.

I've tested @wordpress/env 4.2.0 with docker and it's working as expected.

[espellcaste]

Looks good!

[imath]

In 13249:

Update PHPUnit GH action wp-env & wp-phpunit

See #8628

[imath]

In 13250:

GitHub Action: use composer update rather then install

See #8628

[imath]

In 13251:

revert composer.lock to r13248

See #8628

[imath]

In 13252:

Generate composer.lock using composer install

See #8628

[imath]

In 13253:

Add yoast/phpunit-polyfills to composer required dependencies

See #8628

[imath]

This was more a pain than I was expected! But It's fixed.