lib: Introduce WpSettings API

- WpSettings is a singleton object which attaches itself to the core
  and registry, it provides a get_instance () for its clients.
- WpSettings provides API to get/set wireplumber settings and rules.
- main.c loads the new object and makes sure it is available for
  for all the modules and scripts. This is achieved by introducing
  a new activation step.
- Add the lua bindings for get_setting API.

modules/module-lua-scripting/api/api.c

@@ -1472,6 +1472,26 @@ impl_module_new (lua_State *L)
   }
 }
 
+static int
+get_setting (lua_State *L)
+{
+  const char *setting = luaL_checkstring (L, 1);
+  WpSettings *s = wp_settings_get_instance (get_wp_core (L));
+  if (s)
+  {
+    gboolean value = wp_settings_get_boolean (s, setting);
+    lua_pushboolean (L, value);
+  }
+  else
+    lua_pushnil (L);
+  return 1;
+}
+
+static const luaL_Reg settings_methods[] = {
+  { "get_setting", get_setting },
+  { NULL, NULL }
+};
+
 void
 wp_lua_scripting_api_init (lua_State *L)
 {
@@ -1492,6 +1512,9 @@ wp_lua_scripting_api_init (lua_State *L)
   luaL_newlib (L, plugin_funcs);
   lua_setglobal (L, "WpPlugin");
 
+  luaL_newlib (L, settings_methods);
+  lua_setglobal (L, "WpSettings");
+
   wp_lua_scripting_pod_init (L);
   wp_lua_scripting_json_init (L);
 

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

@@ -210,4 +210,6 @@ SANDBOX_EXPORT = {
   State = WpState_new,
   LocalModule = WpImplModule_new,
   ImplMetadata = WpImplMetadata_new,
+  Settings = WpSettings,
+  I18n = I18n
 }