luci-lua-runtime: dispatcher.lua: re-add post_on() dispatch action

Existing legacy Lua controllers still use the `post_on()` node dispatch
action, so restore this functionality.

Fixes: #6531
Signed-off-by: Jo-Philipp Wich <jo@mein.io>

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

@@ -386,16 +386,20 @@ function call(name, ...)
 	}
 end
 
-function post(name, ...)
+function post_on(params, name, ...)
 	return {
 		["type"] = "call",
 		["module"] = __controller,
 		["function"] = name,
 		["parameters"] = select('#', ...) > 0 and {...} or nil,
-		["post"] = true
+		["post"] = params
 	}
 end
 
+function post(...)
+	return post_on(true, ...)
+end
+
 function view(name)
 	return {
 		["type"] = "view",