[Meta] Introduce a static code analyzer (like PHPStan) to the build process #25459
Description
| Q | A |
|---|---|
| Bug report? | no |
| Feature request? | yes |
| BC Break report? | no |
| RFC? | yes |
| Symfony version | master |
Having a tool like PHPStan introduced to the build process would mean we'd be able to have much more instances like #21802 caught all over the codebase. It would require fewer resources doing code reviews as plenty of thing will get pointed out by PHPStan before even getting to the review process.