[CodeQuality] Add CallbackSingleAssertToSimplerRector to simplify single-assert callback matchers in with()

[TomasVotruba]

Adds CallbackSingleAssertToSimplerRector.

A ->with() callback matcher that only does a single assertSame() + return true; is just a verbose equalTo(). This rule collapses it to the native matcher.

 $builder->expects($this->exactly(2))
     ->method('add')
-    ->with($this->callback(function ($type): bool {
-        $this->assertSame(TextType::class, $type);
-
-        return true;
-    }));
+    ->with($this->equalTo(TextType::class));

Handles multiple with() args independently.

Skips when the callback does more than assertSame() + return true; (a different assert, extra statements, or a non-true return), so matcher behavior is preserved.

Registered in the phpunit-code-quality set.

---

Also loops all with() args in the sibling SimplerWithIsInstanceOfRector (was first-arg only), so assertInstanceOf callbacks convert in any position:

-->with($this->callback(function ($event): bool {
-    $this->assertInstanceOf(UpdateColumnEvent::class, $event);
-    return true;
-}))
+->with($this->isInstanceOf(UpdateColumnEvent::class))