[HttpKernel] [FrameworkBundle] - Added interface to register commands instead of depending on Bundle class

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

- [ ] submit changes to the documentation

This feature introduce a new interface to trigger the registration of commands on Bundles that do not extends `Symfony\Component\HttpKernel\Bundle\Bundle`.

Using this PR, Bundles can now implement `Symfony\Component\HttpKernel\Bundle\BundleInterface` and `Symfony\Component\HttpKernel\Bundle\CommandRegisterInterface` to enable command register by the FrameworkBundle's Application class.

you could use an interface extending both interfaces instead of a class implementing them. You will still be able to mock it, and it will require less code (and with better mocking tools, such extra interface will not be needed at all, but Prophecy is only shipped in the dev version of PHPUnit, not yet in stable ones).