Asynchronous process reaping (#1412)

* refactor(process): introduce process_stream_handle separate from process_handle

* feat(process): introduce process_handle helper functions

* feat(process): add asynchronous process reaping

* feat(process): wait for shorter period if possible

* style(process): remove unecessary brackets

* style(process): fix parentheses

* refactor(process): remove useless setvbuf call

* style(process): remove unecessary value

* refactor(process): add size field into kill_list

* refactor(process): use SDL_Delay for sleeping

* style(process): remove trailing whitespace

* fix(main): destroy window before closing lua

* fix(process): check for timeout correctly

* refactor(process): remove unecessary if check

* refactor(process): remove size from the list

* fix(process): fix invalid delay calculation

Co-authored-by: Guldoman <giulio.lettieri@gmail.com>

---------

Co-authored-by: Guldoman <giulio.lettieri@gmail.com>

src/main.c

@@ -255,8 +255,10 @@ init_lua:
     goto init_lua;
   }
 
-  lua_close(L);
+  // This allows the window to be destroyed before lite-xl is done with
+  // reaping child processes
   ren_free_window_resources(&window_renderer);
+  lua_close(L);
 
   return EXIT_SUCCESS;
 }