Modernize bundle structure (and save the planet)

[loic425]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Related tickets
License	MIT

https://symfony.com/doc/current/bundles/best_practices.html#directory-structure

[alexander-yakushev]

I've never seen anything atom-related showing up in the profile of ring-handler, so I don't think this would give any visible improvement.

[kachayev]

@alexander-yakushev Well... most probably it would not, comparing to other parts of the handler. But it's the same story as we had in #378: when you can do less work, you most certainly should.