Allow casts with a return type of static or this to reference themselves (#1103)

* Allow casts with a return type of static or this to reference themselves

Supports

```php
/**
     * @param $model
     * @param string $key
     * @param $value
     * @param array $attributes
     * @return static
     */
    public function get($model, string $key, $value, array $attributes)
    {
        return new static($value);
    }
```

or

```php
/**
     * @param $model
     * @param string $key
     * @param $value
     * @param array $attributes
     * @return $this
     */
    public function get($model, string $key, $value, array $attributes)
    {
        return new static($value);
    }
```

* Update CHANGELOG.md

src/Console/ModelsCommand.php

@@ -1089,13 +1089,17 @@ class ModelsCommand extends Command
 
         $methodReflection = new \ReflectionMethod($type, 'get');
 
-        $type = $this->getReturnTypeFromReflection($methodReflection);
+        $reflectionType = $this->getReturnTypeFromReflection($methodReflection);
 
-        if ($type === null) {
-            $type = $this->getReturnTypeFromDocBlock($methodReflection);
+        if ($reflectionType === null) {
+            $reflectionType = $this->getReturnTypeFromDocBlock($methodReflection);
+        }
+        
+        if($reflectionType === 'static' || $reflectionType === '$this') {
+            $reflectionType = $type;
         }
 
-        return $type;
+        return $reflectionType;
     }
 
     protected function getTypeInModel(object $model, ?string $type): ?string