The `Type` class was introduced in https://github.com/rails/rails/pull/23085
for the sole purpose of breaking the dependency of Action View on Action Dispatch.

Unless you are somehow running Action View standalone, this is actually
never used.

So instead of delegating, we can use constant swapping, this saves us
a useless layer.

Ultimately we could consider moving `Mime::Types` into Active Support
but it requires some more thoughts.