Add support for PHP 8.3+ and integrate AMPHP executor

[bpteam]

This pull request introduces several enhancements and improvements to the project, focusing on extending PHP version support, integrating async execution with amphp v3, and improving compatibility and testing. The update also includes some minor code quality improvements and dependency updates.

Key changes:

Platform and Dependency Support:

• Extended PHP version support to include PHP 8.3, 8.4, and 8.5 in the CI workflow and updated the composer.json to require PHP ^8.3 and axtiva/flexible-graphql-php ^3.0.2. [1] [2]
• Added amphp/amp as a development dependency and suggested package for async execution support.
• Updated the changelog to reflect support for new PHP versions, ampphp executor integration, and other enhancements.

Async Execution and amphp v3 Integration:

• Added support for amphp v3 executor, including a new test to ensure generated code wraps resolvers with \Amp\async() and not the deprecated \Amp\call().
• Updated test provider to include amphp v3 variants for both GraphQL and federation modes.

Symfony Console Command Registration:

• Simplified console command registration in the dependency injection extension by removing explicit command name tags, relying on Symfony's default command name discovery.
• Added explicit void return type to configure() methods in command classes for better code clarity and type safety. [1] [2] [3]