Remove many function pointer casts

In C it is undefined behavior to call a function through a function pointer of a different type. This is now detected by the Control Flow Integrity Sanitizer. All known issues have already been fixed. Prevent any accidental re-introduction by removing function pointer casts when defining services. The services will call the service functions through the function pointers on the service. As a result the functions must have the same type so there should be no need to cast. Removing the casts allows compilers to warn about assignment to an incompatible function pointer type.