Deprecate magic setters and getters for Events

[juniwalk]

Deprecate __set / __get / __isset magic methods as they cause more issues than is worth.

Explore alternative of __call magic method to setters if it causes the same issues.

// Standard way of adding event listener
$form->when('render', fn() => $form->setService($service), 0);

// Deprecated way of adding event listener
$form->onRender[0] = fn() => $form->setService($service);

// Possible way of adding event listener
$form->onRender(0, fn() => $form->setService($service));