feature #13086 [Console] Define isVerbose(), etc. methods in OutputInterface (frne)

This PR was squashed before being merged into the 3.0-dev branch (closes #13086).

Discussion
----------

[Console] Define isVerbose(), etc. methods in OutputInterface

Could / should the ```Symfony\Component\Console\Output\OutputInterface``` define the methods ```isQuiet()```, ```isVerbose()```, ```isVeryVerbose()``` and ```isDebug()```?

Because the Interface already defines the verbosity constants and the ```getVerbosity()``` method, it will probalby be the right place to do so...

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

Commits
-------

1ac95b1 [Console] Define isVerbose(), etc. methods in OutputInterface

src/Symfony/Component/Console/Output/OutputInterface.php

@@ -75,6 +75,34 @@ interface OutputInterface
      */
     public function getVerbosity();
 
+    /**
+     * Returns whether verbosity is quiet (-q)
+     *
+     * @return bool true if verbosity is set to VERBOSITY_QUIET, false otherwise
+     */
+    public function isQuiet();
+
+    /**
+     * Returns whether verbosity is verbose (-v)
+     *
+     * @return bool true if verbosity is set to VERBOSITY_VERBOSE, false otherwise
+     */
+    public function isVerbose();
+
+    /**
+     * Returns whether verbosity is very verbose (-vv)
+     *
+     * @return bool true if verbosity is set to VERBOSITY_VERY_VERBOSE, false otherwise
+     */
+    public function isVeryVerbose();
+
+    /**
+     * Returns whether verbosity is debug (-vvv)
+     *
+     * @return bool true if verbosity is set to VERBOSITY_DEBUG, false otherwise
+     */
+    public function isDebug();
+
     /**
      * Sets the decorated flag.
      *