Added new fluent PHP config formats for services and routes

[javiereguiluz]

• Services: [DI] Add "PHP fluent format" for configuring the container symfony#23834
• Routes: [Routing] Add PHP fluent DSL for configuring routes symfony#24180

We must make a decision about this:

1. Publish a new article mentioning this new notation ...
2. ... or adding this new format to EVERY example of the docs (this would be a huge task!)

[afurculita]

+1 for adding this new format to EVERY example of the docs

[HeahDude]

This feels needed somehow https://github.com/symfony/symfony-docs/pull/11085/files#diff-7b2545dd61a3817c08117d17725de110L63.

[afilina]

@javiereguiluz @HeahDude Do you guys need help on that?

[xabbuh]

#10824 does the DI part

[HeahDude]

And #11085 did the routing part. Closing here, thanks!