Improve performance for supporting Laravel 8.77+ cast attributes (#1292)

#1289 calls `getReturnType` for every method on every model, which in
turn calls `getReturnTypeFromDocBlock` which has this code:
```php
$phpDocContext = (new ContextFactory())->createFromReflector($reflection);
```
Extracting the docblock is super slow, always has been. Now that we do
this for every method, this adds up a lot.

Performance on a private commercial project _before_ #1289 was introduced:
```
$ time ./artisan ide-helper:models --write --reset >/dev/null

real	0m2.857s
user	0m1.835s
sys	0m0.129s
```
After #1289 :
```
$ time ./artisan ide-helper:models --write --reset >/dev/null

real	0m54.147s
user	0m47.132s
sys	0m1.047s
```

However, in this case we **do not need** the phpdoc fallback (which is
legitimate and by design for many other cases), because also the Laravel
implementation only works by inspecting the _actual type_, see
https://github.com/laravel/framework/blob/e0c2620b57be6416820ea7ca8e46fd2f71d2fe35/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php#L570-L575
```php
$returnType = (new ReflectionMethod($this, $method))->getReturnType();

return static::$attributeMutatorCache[get_class($this)][$key] = $returnType &&
            $returnType instanceof ReflectionNamedType &&
            $returnType->getName() === Attribute::class &&
            is_callable($this->{$method}()->get);
```

This side-stepping the phpdoc parsing a) still works correctly and b)
brings us back to the previous performance characteristics:
```
time ./artisan ide-helper:models --write --reset >/dev/null

real	0m2.987s
user	0m1.915s
sys	0m0.120s
```

tests/Console/ModelsCommand/Attributes/Models/Simple.php

@@ -20,4 +20,24 @@ class Simple extends Model
             }
         );
     }
+
+    /**
+     * ide-helper does not recognize this method being an Attribute
+     * because the method has no actual return type;
+     * phpdoc is ignored here deliberately due to performance reasons and also
+     * isn't supported by Laravel itself.
+     *
+     * @return \Illuminate\Database\Eloquent\Casts\Attribute
+     */
+    public function notAnAttribute()
+    {
+        return new Attribute(
+            function (?string $value): ?string {
+                return $value;
+            },
+            function (?string $value): ?string {
+                return $value;
+            }
+        );
+    }
 }