* Bump PHPUnit dependencies
* Set return type of base TestCase methods
From the [PHPUnit 8 release notes][1], the `TestCase` methods below now declare a `void` return type:
- `setUpBeforeClass()`
- `setUp()`
- `assertPreConditions()`
- `assertPostConditions()`
- `tearDown()`
- `tearDownAfterClass()`
- `onNotSuccessfulTest()`
[1]: https://phpunit.de/announcements/phpunit-8.html
* Ignore PHPUnit cache folder
* Adopt PHP attributes in test classes
* Declare data providers as `static`
* Add return types to test methods
* Define test classes as `final`
* Migrate phpunit.xml to phpunit 10
* Correct phpunit attribute class name
* Rename base test class
* Restructure test folders
* Fix test image paths
* Only set rules for php files in .editorconfig
* Remove php unit flag in local test env
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Co-authored-by: Shift <shift@laravelshift.com>
