Support code for generating enhancer/fast-class glue.

Each glue class has a trampoline that accepts an index, context object, and argument array:

public static Object GUICE$TRAMPOLINE(int index, Object context, Object[] args) {
  switch (index) {
    case 0: {
      return ...;
    }
    case 1: {
      return ...;
    }
  }
  return null;
}

Each indexed statement in the trampoline invokes a constructor or method, returning the result. The expected context object depends on the statement; it could be the invocation target, some additional constructor context, or it may be unused. Arguments are unpacked from the array onto the call stack, unboxing or casting them as necessary. Primitive results are autoboxed before being returned.

Where possible the trampoline is converted into a lookup Function mapping an integer to an invoker function, each invoker represented as a BiFunction that accepts a context object plus argument array and returns the result. These functional interfaces are used to avoid introducing a dependency from the glue class to Guice specific types. This means the glue class can be loaded anywhere that can see the host class, it doesn't need access to Guice's own ClassLoader. (In other words it removes any need for bridge ClassLoaders.)