Refactor the tests for newer Phpunit version

[Zvax]

After the nullable typehint PR, there's been a few commits to bump the PHP version, normalize test namespace and move towards github actions.

This PR attempts to update the testsuite to best accommodate these changes, though I have made some judgement calls:

1. I've bumped the phpunit version to >= 7, such that php versions will be able to resolve the composer file. using ^7 or ^8 would fail either on 8.x or <=7.1
2. I've replaced the fabpot/php-cs-fixer with the recommended package visible in the composer commands, that is friendsofphp/php-cs-fixer. I've renamed the config file as advised, though unsure what should be the new config, and there doesn't seem to be evident configs in the ecample file https://github.com/PHP-CS-Fixer/PHP-CS-Fixer/blob/master/.php-cs-fixer.dist.php
3. Change the 'Auryn\Type' strings to Type::class invocations where pertinent
4. refactor the deprecated @expectException comments to $this->expectException and related calls
5. Add some checks on the phpversion to account for the change of behaviour of the Class not found php exception message (from php > 8 class is surrounded by double wuotes)
6. added explicit properties where implicit property declaration was tripping tests
7. slapped a bunch of assertTrue(true) where tests were saying having no assertions. I presume if the rest of the tests didn't throw then we consider it valid.
8. add return types to the tests

I've went as far as I could with solving the tests, however on 8.x suites there are a few failures that necessitate a better knowedge of what should happen than I possess (please see https://github.com/Zvax/auryn/actions/runs/12017589097). I think they are related, it seems like the nullable instances with default values aren't being passed, or something.

There were 4 failures:

1) Auryn\InjectorTest::testNonConcreteDependencyWithDefaultValueThroughAlias
Failed asserting that null is an instance of class "Auryn\ImplementsInterface".

/home/runner/work/auryn/auryn/test/InjectorTest.php:765

2) Auryn\InjectorTest::testNonConcreteDependencyWithDefaultValueThroughDelegation
Failed asserting that null is an instance of class "Auryn\ImplementsInterface".

/home/runner/work/auryn/auryn/test/InjectorTest.php:774

3) Auryn\InjectorTest::testDependencyWithDefaultValueThroughShare
Failed asserting that null is an instance of class "StdClass".

/home/runner/work/auryn/auryn/test/InjectorTest.php:788

4) Auryn\InjectorTest::testDelegationDoesntMakeObject
Failed asserting that exception of type "TypeError" matches expected exception "Auryn\InjectionException". Message was: "class_implements(): Argument #1 ($object_or_class) must be of type object|string, null given" at
/home/runner/work/auryn/auryn/lib/Injector.php:596
/home/runner/work/auryn/auryn/lib/Injector.php:376
/home/runner/work/auryn/auryn/test/InjectorTest.php:1123

As far as I can teel this seems like the behaviour actually changes so I don't know what should be changed.

Please let me know if/how these should be fixed.

[kelunik]

Thanks! Why did you close this?

[Zvax]

after I realized I was spamming everyone with my test runs, I wanted to close it until I could make the runs pass. Please see the updated passing PR!