Issue #3619703: Fix the cspell failures caused by the core 11.4.5 dictionary (2.0.x backport)

Closes #3619703

Drupal 11.4.5 dropped eleven Composer vendor and package names from core/misc/cspell/dictionary.txt as part of #3607061, and this project uses two of them.

• PHP Codesniffer becomes PHP CodeSniffer, the tool's own spelling. cspell splits that into two words it already knows, so it needs no dictionary entry.
• codesniffer and mglaman go into .cspell-project-words.txt, for the two occurrences that are Composer package names and cannot be spelled any other way. This branch's word list is not in alphabetical order, so they are appended rather than inserted.

Checked with cspell 9.8.0 against the 11.4.5 dictionaries: the reported words are gone.

Also carries the phpstan (previous major): rules: - when: never override that 4.x, 3.x and 3.0.x already have, so phpstan runs on the current version only. 2.0.x was the one branch still missing it.