* 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
Sample39 was not adjusted when Defined Name support was changed to include both relative and absolute addresses. As a result, the Xlsx output is currently incorrect. The Xls output is in even worse shape, since PhpSpreadsheet 'Cannot yet write formulae with defined names to Xls' (see Writer/Xls/Parser.php). (Working around that restriction was the reason for my first contribution to this project.) The sample is changed to define its named ranges properly, and to produce only Xlsx output.