Rethink the way the error handler works

[Tofandel]

Fixes #2607

We can use the user provided handler and simply add render cases via methods, so we don't need to provide our own exception handler, which will alleviate the need for more configuration/setup when installing twill

I also optimized the provider to have all the config in one place and not have it run if the config is already cached

[ifox]

This is great @Tofandel thank you. The custom exception handler has definitely been a source of issues and this approach is so much better.