Added GeoClue2 privacy item

Rebased onto current master and fixed the privacy module build:
- privacy_item.hpp no longer includes privacy.hpp (it does not use the
  Privacy class); this broke the circular include that left PrivacyItem
  undeclared when privacy.hpp was reached first from privacy_item.cpp.
- privacy_item.cpp now includes gtkmm/label.h explicitly, since Gtk::Label
  was previously only pulled in transitively via privacy.hpp.

src/util/pipewire/privacy_node_info.cpp

@@ -2,7 +2,7 @@
 
 namespace waybar::util::PipewireBackend {
 
-std::string PrivacyNodeInfo::getName() {
+std::string PWPrivacyNodeInfo::getName() {
   const std::vector<std::string*> names{&application_name, &node_name};
   std::string name = "Unknown Application";
   for (const auto& item : names) {
@@ -15,7 +15,7 @@ std::string PrivacyNodeInfo::getName() {
   return name;
 }
 
-std::string PrivacyNodeInfo::getIconName() {
+std::string PWPrivacyNodeInfo::getIconName() {
   const std::vector<std::string*> names{&application_icon_name, &pipewire_access_portal_app_id,
                                         &application_name, &node_name};
   std::string name = "application-x-executable-symbolic";
@@ -27,12 +27,12 @@ std::string PrivacyNodeInfo::getIconName() {
   return name;
 }
 
-void PrivacyNodeInfo::handleProxyEventDestroy() {
+void PWPrivacyNodeInfo::handleProxyEventDestroy() {
   spa_hook_remove(&proxy_listener);
   spa_hook_remove(&object_listener);
 }
 
-void PrivacyNodeInfo::handleNodeEventInfo(const struct pw_node_info* info) {
+void PWPrivacyNodeInfo::handleNodeEventInfo(const struct pw_node_info* info) {
   state = info->state;
 
   const struct spa_dict_item* item;