Remove number of arguments from defining Dart FFI (#50153)

The number of arguments are not used. 

And also, even if we need it in the future, they can be derived at compile time:

```cpp
template <typename T>
struct function_traits;

template <typename Ret, typename... Args>
struct function_traits<Ret(Args...)>
{
    using params = std::tuple<Args...>;
};

template <typename T>
constexpr std::size_t get_parameter_count() {
    return std::tuple_size<typename function_traits<T>::params>::value;
}

template <typename T>
struct member_function_traits;

template <typename C, typename Ret, typename... Args>
struct member_function_traits<Ret(C::*)(Args...)>
{
    using params = std::tuple<Args...>;
};

template <typename T>
constexpr std::size_t get_member_function_parameter_count() {
    return std::tuple_size<typename member_function_traits<T>::params>::value;
}

```

(I got the code above with ChatGPT but I verified that they work)

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: dkwingsmt

fml/platform/fuchsia/log_interest_listener.h

@@ -34,4 +34,4 @@ class LogInterestListener {
 
 }  // namespace fml
 
-#endif  // FLUTTER_FML_PLATFORM_FUCHSIA_LOG_STATE_H_
+#endif  // FLUTTER_FML_PLATFORM_FUCHSIA_LOG_INTEREST_LISTENER_H_

fml/platform/fuchsia/log_state.h

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef FLUTTER_FML_PLATFORM_FUCHSIA_LOG_CONNECTION_H_
-#define FLUTTER_FML_PLATFORM_FUCHSIA_LOG_CONNECTION_H_
+#ifndef FLUTTER_FML_PLATFORM_FUCHSIA_LOG_STATE_H_
+#define FLUTTER_FML_PLATFORM_FUCHSIA_LOG_STATE_H_
 
 #include <fidl/fuchsia.logger/cpp/fidl.h>
 #include <lib/fidl/cpp/wire/internal/transport_channel.h>
@@ -52,4 +52,4 @@ class LogState {
 
 }  // namespace fml
 
-#endif  // FLUTTER_FML_PLATFORM_FUCHSIA_LOG_CONNECTION_H_
+#endif  // FLUTTER_FML_PLATFORM_FUCHSIA_LOG_STATE_H_