Refactor WebhookSignatureValidation for improved signature validation and certificate management

- Enhanced the validate method to streamline error handling and improve readability.
- Introduced separate methods to determine the appropriate certificate based on the current date and environment.
- Updated logic for determining the filename of the certificate to accommodate future certificates.
- Improved exception handling for loading keys and verifying signatures.

Author: DaanRijpkema

composer.json

@@ -47,7 +47,6 @@
     },
     "require-dev": {
         "squizlabs/php_codesniffer": "^3.10",
-        "magento/magento-coding-standard": "^31.0",
         "phpunit/phpunit": "^12",
         "phpspec/prophecy": "~1.0",
         "vlucas/phpdotenv": "^5.6",