Refactor Request object documentation and redefine method logic

[Spomky]

Fixes #19748

The documentation for the Request object in the controller documentation has been updated to be more specific. The logic of the getPreferredLanguage method has been updated and clarified in Symfony 7.1. An additional step has been added which accounts for languages that match the locale, but exhibit a different script or region. The Response Object section has been moved for better flow and readability.

[javiereguiluz]

Florent, thanks a lot for this contribution. However, I changed it a lot while merging it.

On 6.4 branch:

• I removed these contents from controller.rst and moved them to a new section in translation.rst
• I added a short example of using the method and passing the array of arguments for clarity
• I removed the detailed list that explains all the steps run internally by this method. Your original content is perfectly correct ... but while merging it I realized that it was too detailed. It describes the internal code almost line by line. So, I reworded the entire behavior as a short phrase.

See a293225

On 7.1 branch:

• I reworded the explanation to mention that in addition to "perfect match" now Symfony also tries "partial match" based on the language part of the locale

See d0fd14b

I'm sorry I changed your contribution so much. We usually only tweak users' contributions ... but this time I felt like we had to make more changes. Sorry!

[Spomky]

Thank you @javiereguiluz.
One question though: why 6.4? The PR was merged in 7.1.

[javiereguiluz]

Yes, I missed something in my previous comment: I merged it in 6.4 (but not the 7.1 addition) because in the docs we were really missing this explanation about preferred languages.

[Spomky]

Cristal clear. No problem.
Juss tell me if you want me to add anything else.