fix: make robust c++ type deduce

[devillove084]

Completely remove template specialization code: Modern C++ compilers (supporting C++20 coroutines) can automatically infer promise_type. Rely on automatic lookup mechanism: As long as the RustPromise class defines the correct coroutine interface, the compiler can find it.

FIX: Avoid problems with complex macro generation and template specialization

Why does this solution work?

• C++20 coroutines will automatically look for the promise_type of the return type
• The RustPromise class has implemented all interfaces required for coroutine promises
• Avoid error-prone template specialization and macro generation
• Fully compliant with the C++20 coroutine specification