[EventDispatcher] Added TraceableEventDispatcher from HttpKernel
feature #9814 [EventDispatcher] Added TraceableEventDispatcher from HttpKernel (florianv)

This PR was merged into the 2.5-dev branch.

Discussion
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[EventDispatcher] Added TraceableEventDispatcher from HttpKernel

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Moved the reusable parts from the `TraceableEventDispatcher` from `HttpKernel` to the same class in `EventDispatcher` to allow debugging dispatchers.

I changed the `TraceableEventDispatcherInterface` to extend `EventDispatcherInterface`, so this is a BC break but I'm not sure if a lot of people use it without actually extending it.

Commits
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9a90e06 [EventDispatcher] Added TraceableEventDispatcher from HttpKernel