Makes lua file upload work with bigger files and standardizes a few file|null (#82202)

## About The Pull Request
My lua scripts were hitting the topic byte limit, so this makes file
upload of lua scripts able to bypass the topic limit.

## Why It's Good For The Game
Removes arbitrary restriction on how big a lua file can be in bytes.

## Changelog
🆑
admin: Admins can now run lua files bigger than 36 KB by importing them
directly.
/🆑

Co-authored-by: Watermelon914 <3052169-Watermelon914@users.noreply.gitlab.com>

code/modules/admin/verbs/lua/lua_editor.dm

@@ -105,6 +105,11 @@
 		return
 	if(!check_rights_for(usr.client, R_DEBUG))
 		return
+	if(action == "runCodeFile")
+		params["code"] = file2text(input(usr, "Input File") as null|file)
+		if(isnull(params["code"]))
+			return
+		action = "runCode"
 	switch(action)
 		if("newState")
 			var/state_name = params["name"]