[FrameworkBundle] Enable controller service with #[Route] attribute

[fabpot]

Q	A
Feature PR	symfony/symfony#60081
PR author(s)	@GromNaN
Merged in	7.3

We created this issue to not forget to document this new feature. We would really appreciate if you can help us with this task. If you are not sure how to do it, please ask us and we will help you.

To fix this issue, please create a PR against the 7.3 branch in the symfony-docs repository.

Thank you! 😃

[GromNaN]

Update How to Define Controllers as Services to show that, by default, every service that uses the #[Route] attribute is registered as a controller (public, non-lazy, and service argument injection). #[AsController] attribute is necessary only when routes are defined in Yaml/Xml/PHP config files.