Do not lose _route_params

[VincentLanglet]

Subject

I am targeting this branch, because bugfix.

This is an attempt to fix #7185

Changelog

### Fixed
- childId are not lost anymore when using multiple times the appendFormFieldAction and similar actions.

[VincentLanglet]

How do i have the app variable in tests @sonata-project/contributors ?

[franmomu]

this is not needed anymore?

[VincentLanglet]

It's already inside the app.request.query.all value.

[franmomu]

One question, would it be enough to generate the id, childId, etc parameters from the admin and attach them (with an extension or something as you said at the beginning)? or not because they are not the same?

My concern is about adding parameters that are not really needed.

[VincentLanglet]

One question, would it be enough to generate the id, childId, etc parameters from the admin and attach them (with an extension or something as you said at the beginning)? or not because they are not the same?

It would be enough for my case.

My concern is about adding parameters that are not really needed.

Yes I understand. But thinking about it, I was wondering "What is a not needed parameter ?"
For instance, you could have some specific logic about the query parameters in your admin class (which is already the case with persistent parameters). So since all the query params could be used in your admin class to have a specific behavior, I didn't find this as a bad idea to keep them all.