ControllerEmu is a massive class with a lot of nested public classes.
The only reason these are nested is because the outer class acts as a
namespace. There's no reason to keep these classes nested just for that.
Keeping these classes nested makes it impossible to forward declare them, which leads to quite a few includes in other headers, making compilation take
longer.
This moves the source files to their own directory so classes can be
separated as necessary to their own source files, and be namespaced under the
ControllerEmu namespace.
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