Better formatter auto-discovery in FakeItEasy 1.13.0

A few weeks ago, I wrote about the problems that FakeItEasy's assembly scanning was causing while it was looking for user-defined extensions. To recap, FakeItEasy was scanning all assemblies in the AppDomain and the working directory, looking for types that implemented IArgumentValueFormatter, IDummyDefinition, or IFakeConfigurator. This process was quite slow …