Fix caching issues

[uuf6429]

Fixes #18.

• Add cache integration test
• Ensure test fails in older situation and passes with the fix
• Fix AbstractFormatter:

  abstract class AbstractFormatter implements JsonSerializable
  ...
  /**
   * @return array<string, mixed>
   */
  public function jsonSerialize(): array
  {
      return ['class' => static::class, 'version' => $this->version];
  }

• Override jsonSerialize() in child formatters to provide details about the formatter (e.g. to distinguish between cli formatters with same class, different command)
• Prepare for major version release, since changes are not backward compatible.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
54	1	53	1

View the top 1 failed test(s) by shortest run time

uuf6429.PhpCsFixerBlockstringTests.Integration.CacheTest::testCacheReuse with data set #2

Stack Traces | 0.582s run time

uuf6429\PhpCsFixerBlockstringTests\Integration\CacheTest::testCacheReuse with data set #2 ('Test v2', 'Fixed 1 of 1 files', 'Cache file existed already')
Failed asserting that 'You are running PHP CS Fixer on PHP 8.4.21, but the minimum PHP version supported by your project in composer.json is PHP 7.4. Executing PHP CS Fixer on newer PHP versions may introduce syntax or features not yet available in PHP 7.4, which could cause issues under that version. It is recommended to run PHP CS Fixer on PHP 7.4, to fit your project specifics.\n
If you need help while solving warnings, ask at https://github..../PHP-CS-Fixer/PHP-CS-Fixer/discussions/, we will help you!\n
\n
PHP CS Fixer 3.95.2 Adalbertus by Fabien Potencier, Dariusz Ruminski and contributors.\n
PHP runtime: 8.4.21\n
Loaded config default from ".../tests/Integration/../fixtures/simple-config.php".\n
Running analysis on 1 core sequentially.\n
Using cache file ".../_nsk_h4s1kng41z5pgfbx7sh0000gn/T/pcf-cache-test-6a0f599ce63027.79160952/cache.json".\n
\n
Fixed 0 of 1 files in 0.005 seconds, 16.00 MB memory used\n
' contains "Fixed 1 of 1 files".

.../tests/Integration/CacheTest.php:79

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