[8.x] Accept callable class for reportable and renderable in exception handler

[smujaddid]

In its current implementation, as the reportable and renderable callbacks are handled by depending on ReflectClosure's firstClosureParameterType call, the callable parameter type in both method can not accept a callable class such as:

use My\CustomException;

class CustomReporter
{
    public function __invoke(CustomException $e)
    {
        // Do whatever here
    }
}

class CustomRenderer
{
    public function __invoke(CustomException $e, $request)
    {
        return response()->json(['message' => 'The CustomRenderer response']);
    }
}

and in exception handler:

public function register()
{
    $this->reportable(new CustomReporter());
    $this->renderable(new CustomRenderer());
}

This PR will allow this to happen as any class with __invoke() implemented can be passed into both reportable and renderable, and probably any other callable as long as it accepted by Closure::fromCallable().