luci-lua-runtime: dispatcher.lua: translate legacy node "target" property

Some legacy Lua controllers declare menu entries by first invoking `node()`
and then setting the `.target` property on the resulting object.

Make sure to properly translate such menu nodes into the internal menu
JSON representation.

Fixes: #6090
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-lua-runtime/luasrc/dispatcher.lua

@@ -186,6 +186,11 @@ function process_lua_controller(path)
 			entry.auth = {}
 		end
 
+		if entry.action == nil and type(entry.target) == "table" then
+			entry.action = entry.target
+			entry.target = nil
+		end
+
 		entry.leaf = nil
 
 		entry.file_depends = nil