[FrameworkBundle] Add shortcut methods to controllers

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11166
| License       | MIT
| Doc PR        | 

To-do list : 
- [x] submit changes to the documentation

Added redirectToRoute, addFlash, isGranted and checkGranted to controllers. The code seems so simple I didn't feel like adding controller tests was needed since we're just shortcuting other services calls.
Just found issue about it so I'll cross-reference it: https://github.com/symfony/symfony/issues/11279 - anyway I think that some ``FlashAwareSessionInterface`` isn't bad. However it's not up to me, just saying :)