Use native PHPDocs for Rule and RuleTestCase

[paulbalandan]

I'm using intelephense in VS Code and it cannot understand the @phpstan- annotated PHPDocs. However, it understands the native PHPDocs, including the generics related. This PR uses those PHPDocs for Rule and RuleTestCase for better IDE completion on vscode.

Proof:

[ondrejmirtes]

Thank you.

[paulbalandan]

Thanks for merging this. Would you be ok for follow up PRs that (1) removes similar @phpstan- annotated PHPDocs and replaces them with the native ones, and (2) removes superfluous PHPDocs due to better IDE completions, especially in the rules?

[ondrejmirtes]

We need to acknowledge this isn't fixing anything in PHPStan, but rather addressing a shortcoming of another tool, but I'm okay with this, we don't need any prefixes in PHPDocs here.