CS fixes

[rosier]

I did split this in separate commits to make it easier to review.

I can squash this if you prefer that.

[rosier]

The fabbot suggests a few more changes but I not sure if all work on PHP 7.1

[rosier]

The fabbot suggest one more change but that requires PHP 8

-                if (0 === strpos(\get_class($plugin), 'Hirak\Prestissimo\Plugin')) {
+                if (0 === strpos($plugin::class, 'Hirak\Prestissimo\Plugin')) {

[fabpot]

Thank you @rosier.