Refactor C++ to return Swift::Expected instead of SWIFT_RETURN_THUNK

[Robertorosmaninho]

This is a simple PR to replace the of SWIFT_RETURN_THUNK(T, v) directly by Swift::Expected<T>(v) when it's declared on the #else clause of the #ifdef __cpp_exceptions on the C++ thunk that represents a Swift function on the bridging header.

Example:

• Previously:

inline Swift::ThrowingResult<swift::Int> throwFunctionWithReturn() SWIFT_WARN_UNUSED_RESULT {
    void* opaqueError = nullptr;
    void* _ctx = nullptr;
    auto returnValue = _impl::$s9Functions23throwFunctionWithReturnSiyKF(_ctx, &opaqueError);
#ifdef __cpp_exceptions
    throw (Swift::Error(opaqueError));
#else
    return SWIFT_RETURN_THUNK(swift::Int, Swift::Error(opaqueError));
#endif
    return SWIFT_RETURN_THUNK(swift::Int, returnValue);
}

• Proposed:

inline Swift::ThrowingResult<swift::Int> throwFunctionWithReturn() SWIFT_WARN_UNUSED_RESULT {
    void* opaqueError = nullptr;
    void* _ctx = nullptr;
    auto returnValue = _impl::$s9Functions23throwFunctionWithReturnSiyKF(_ctx, &opaqueError);
#ifdef __cpp_exceptions
    throw (Swift::Error(opaqueError));
#else
    return Swift::Expected<swift::Int>(Swift::Error(opaqueError));
#endif
    return SWIFT_RETURN_THUNK(swift::Int, returnValue);
}

[hyp]

@swift-ci please test