[Console] Added verbosity level shorthand methods to OutputInterface

Hello,

I've added the verbosity level shorthand methods to the interface "Symfony\Component\Console\Output\OutputInterface" as they should always be implemented by classes implementing the interface. Also it makes unit test easier and avoids warnings like:

"The method isVerbose() does not seem to exist on object<Symfony\Compon...put\OutputInterface>." (Scrutinizer-Cis PHP Analyzer)

As this possibly could break backwards compatibility I like to merge into master. 

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | no