wplua: move under modules/module-lua-scripting

It's unlikely that wplua will ever be useful outside the context
of module-lua-scripting, so let's move it to keep all the code in one place

modules/module-lua-scripting/api/gresource.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<gresources>
+  <gresource prefix="/org/freedesktop/pipewire/wireplumber/m-lua-scripting/">
+    <file compressed="true">api.lua</file>
+  </gresource>
+</gresources>