chore: Promote annotations @before and @beforeClass to attributes

[Pixelshaped]

Fix #174

Opening this pull request to solve deprecations happening with PHPUnit 11, such as Metadata found in doc-comment for method SomeClass::erisSetup(). Metadata in doc-comments is deprecated and will no longer be supported in PHPUnit 12. Update your test code to use attributes instead.

• Convert @before and @beforeClass annotations to attributes
• Update the README.md too.
• Update PHPStan baseline, to solve PHPStan errors
• Solve own test deprecations (mostly linked to the @DataProvider annotation)
• Update test matrix to account for PHPUnit11 and PHP8.3

[Pixelshaped]

@giorgiosironi we seem to be in the clear :)

Please tell me if anything else is needed. I made the PR against 1.x.x as my previous one was also merged against that branch instead of master.

[ilario-pierbattista]

@Pixelshaped lgtm, this will become 1.0.0-rc2

again, thank you