fix: fix circularity on JSHandle interface

[jrandolf]

This PR fixes the ongoing problem related to circularity on the JSHandle.

For background, the original implementation attempted to make use of the fact the this object was a JSHandle of type T. Since the EvaluateFunc type flatten handles, it's assumed the compiler could deal with this which it does. However, this causes another problem to arise where the return type is considered self-referencing because the return type is derived from EvaluateFunc<[this,... which looks somewhat like EvaluateFunc<[EvaluateFunc<[EvaluateFunc<[...,...,...,... to the compiler.

Our solution here is to flatten the this value to the actual type we want. This way no inference is needed, so the compile doesn't see the circular type above.