chore: solve PHPUnit 10 deprecations (#918)

* Bump PHPUnit dependencies

* Adopt PHP attributes in test classes

* Declare data providers as `static`

* Add return types to test methods

* Define test classes as `final`

* chore: make static dataproviders work

* chore: attempt to make tests pass on prefer-lowest

* chore: camel case variables

---------

Co-authored-by: Shift <shift@laravelshift.com>

Author: jordyvanderhaegen

composer.json

@@ -21,7 +21,7 @@
     },
     "require-dev": {
         "orchestra/testbench-browser-kit": "^8.5|^9.0",
-        "phpunit/phpunit": "^9.5.10|^10.0"
+        "phpunit/phpunit": "^10.1"
     },
     "suggest": {
         "ext-intl": "*"