[9.x] Allow registering instances of commands (#43986)

* allow registering instances of commands

* add typehint

Author: freekmurze

src/Illuminate/Console/Application.php

@@ -262,7 +262,7 @@ protected function addToParent(SymfonyCommand $command)
     /**
      * Add a command, resolving through the application.
      *
-     * @param  string  $command
+     * @param  \Illuminate\Console\Command|string  $command
      * @return \Symfony\Component\Console\Command\Command|null
      */
     public function resolve($command)
@@ -273,6 +273,10 @@ public function resolve($command)
             return null;
         }
 
+        if ($command instanceof Command) {
+            return $this->add($command);
+        }
+
         return $this->add($this->laravel->make($command));
     }