[DI][FrameworkBundle] Add PSR-11 "ContainerBag" to access parameters as-a-service

[javiereguiluz]

Added PSR-11 ContainerBagInterface and its ContainerBag implementation to access parameters as-a-service. See symfony/symfony#25288

[weaverryan]

Might be a dup of #8999 :)

Btw, I think we should mention ParameterBagInterface, not ContainerBagInterface. I believe they both can be used to access this service, but ParameterBagInterface is a better name.

[javiereguiluz]

Closing as duplicate and I'm going to update the PR to use ParameterBagInterface. Thanks!