A continuation of PR #3859. Change code that would be flagged if we were to run Phpstan at level 9 (we currently run level 8). I may or may not follow up with source code (454 level-9 problems remain for src), but there is no reason to avoid the effort for samples.
No changes are made to src.
* Let Phpstan Run on Samples
Phpstan currently analyzes all source and test members. We already run phpcs and php-cs-fixer on samples as well. I would expect that samples are often used as templates for code in userland; it behooves us to be at least as careful with those members as for the others which are already being analyzed. Aside from 1300+ messages `Variable $helper might not be defined.`, which will be suppressed in phpstan.neon.dist, there are really only a few changes needed for sample members, so that part of the code base was already in good shape, and is now even better. No annotations were needed.
* Scrutinizer 2 out of 3
1 false positive, now suppressed; fix other 2.
* Remove Dead Code
* Very Minor Changes
* Add infra
Because they tend to clutter our code a lot and unfortunately, there are
lots of false positives. Instead, it would probably be better to deal
with false positives out of band, via the Scrutinizer web UI.