PHPUnit 10 Migration (#1302)

* 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

---------

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

tests/Unit/Drivers/Gd/Encoders/JpegEncoderTest.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Intervention\Image\Tests\Unit\Drivers\Gd\Encoders;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\RequiresPhpExtension;
+use Intervention\Image\Drivers\Gd\Core;
+use Intervention\Image\Drivers\Gd\Driver;
+use Intervention\Image\Encoders\JpegEncoder;
+use Intervention\Image\Drivers\Gd\Frame;
+use Intervention\Image\Image;
+use Intervention\Image\Tests\BaseTestCase;
+
+#[RequiresPhpExtension('gd')]
+#[CoversClass(\Intervention\Image\Encoders\JpegEncoder::class)]
+#[CoversClass(\Intervention\Image\Drivers\Gd\Encoders\JpegEncoder::class)]
+final class JpegEncoderTest extends BaseTestCase
+{
+    protected function getTestImage(): Image
+    {
+        return new Image(
+            new Driver(),
+            new Core([
+                new Frame(imagecreatetruecolor(3, 2))
+            ])
+        );
+    }
+
+    public function testEncode(): void
+    {
+        $image = $this->getTestImage();
+        $encoder = new JpegEncoder(75);
+        $result = $encoder->encode($image);
+        $this->assertMediaType('image/jpeg', (string) $result);
+    }
+}