Accept slow tests

[staabm]

I think it would be useful, if this package would provide a attribute which I can put on a test method to explicitly state

• I know this test is slow
• I don't mind when this test takes 10 seconds

that way a user of this package could indicate where slowness is acceptable and known and the tool therefore would be able to easily identify regressions (e.g. when a unit test was fast before and gets slower because of changes)

idea came from this discussion at the php-cs-fixer repo:
PHP-CS-Fixer/PHP-CS-Fixer#9025 (comment)

[staabm]

so for example

indicate that we are fine when this test takes 5-10 seconds

<?php declare(strict_types=1);
final class Greeter
{
    #[SlowTest(min: 5, max: 10)]
    public function greet(string $name): string
    {
        sleep(5);
        return 'Hello, ' . $name . '!';
    }
}

-> this plugin should not list such a test in the overall result, as long as it is slower then 10 seconds