Don't replace the upcasted values in the request attributes array.

While working on #2031473: Convert menu local actions to plugins so that we can generate dynamic titles and paths we realized that the attributes array contains just the upcasted value,
but there are valid usescase where we really need the original value.

Just replace the value won't fly, so the new value has to be stored somewhere else. The idea is to use _converted_$name now.

In order to still allow nice injection into controllers/whatever else, the controller resolver (which is a class which puts arguments from the request and together with the information about the controller, figures out the needed values).

@TODO Better summary.