Symfony 7 support and test against PHP 8.3 & 8.4

A big thanks to @Growiel who finished Symfony 7 support and other contributors who helped to push it forward!

What's Changed

• Use Composer v2 on CI by @bocharsky-bw in #503
• Add PHP 8.3, 8.4 to CI by @andreybolonin in #505
• Apply PHP CS Fixer changes by @bocharsky-bw in #507
• Bump PHP to 8.1 in composer.json by @bocharsky-bw in #506
• Fix CS w/ PHP CS Fixer by @bocharsky-bw in #510
• Support SF7 by @Growiel in #509

New Contributors

• @Growiel made their first contribution in #509

Full Changelog: 0.14.3...0.15.0