…spatcher in debug:event-dispatcher (TimoBakx)

This PR was squashed before being merged into the 5.3-dev branch.

Discussion
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[FrameworkBundle] Added option to specify the event dispatcher in debug:event-dispatcher

| Q             | A
| ------------- | ---
| Branch?       | 5.x
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | N/A
| License       | MIT
| Doc PR        | symfony/symfony-docs#14650
| Tags | #SymfonyHackday

### Description:
In the recent security improvements, new event dispatchers were added (one for each firewall). These were not visible in the `debug:event-dispatcher` command. This PR adds an option to define a event dispatcher to show the events (and listeners) for that specific event dispatcher. Without any options, the default dispatcher is shown (identical to previous working)

In order to be able to fetch specific event dispatchers, I tagged all event dispatchers with a new `kernel.event-dispatcher` tag.

### Usage:
`bin/console debug:event-dispatcher --dispatcher=[servicename] [other options] [event]`

### Subtasks:
- [x] Add `dispatcher` option
- [x] Add `kernel.event_dispatcher` tag to all event dispatchers
- [x] Add autoconfigure tag for services implementing `EventDispatcherInterface`
- [x] Update Descriptor classes to specify the chosen dispatcher
- [x] Update changelog
- [x] Add documentation

Commits
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62398b5 [FrameworkBundle] Added option to specify the event dispatcher in debug:event-dispatcher