Add X-Debug-Url profiler url header

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | None

Hey, working with rest APIs I find it way more convenient to have the profiler url directly in the header ... We human are used to deal with hypermedia!
A little bit of hateoas in symfony :)