Remove and replace C typedefs

`typedef struct/union/enum name { ... } name_again;` is not needed whe compiling C++, moving the name at the back to be in front of the object and removing `typedef` makes it usable the very same way.
This also replaces typedefs with the using keyword. They have better readability, especially for function pointer types, and would allow more flexibility when used with templates.

src/openrct2/network/Http.cpp

@@ -43,7 +43,7 @@ struct HttpRequest2
     void *          Tag = nullptr;
     std::string     Method;
     std::string     Url;
-    http_data_type  Type;
+    HTTP_DATA_TYPE  Type;
     bool            ForceIPv4 = false;
     size_t          Size = 0;
     union
@@ -105,17 +105,17 @@ struct HttpRequest2
     }
 };
 
-typedef struct read_buffer {
+struct read_buffer {
     char *ptr;
     size_t length;
     size_t position;
-} read_buffer;
+};
 
-typedef struct write_buffer {
+struct write_buffer {
     char *ptr;
     size_t length;
     size_t capacity;
-} write_buffer;
+};
 
 void http_init()
 {