feat: Add Essentials Toolbar and hide Accordion Header in compact mode

- Added the Essentials Toolbar to the Navigator Toolbox
- Removed the Essentials Toolbar from ZenStartup and created it in browser-places.js
- Updated the zen-styles/zen-sidebar.css file to remove the display of the Menubar
- Updated the navigator-toolbox.inc.xhtml file to add the Essentials Toolbar and hide the Accordion Header in compact mode
- Updated the indicator-private-browsing.svg file to include the private browsing indicator icon

src/browser/base/content/browser-places-js.patch

@@ -1,5 +1,5 @@
 diff --git a/browser/base/content/browser-places.js b/browser/base/content/browser-places.js
-index 62b3665394a8256ebedf88a8f10bb6766977cf57..a0bee37cbf9e8f79b3ea69b8dec711a93ef837a0 100644
+index 62b3665394a8256ebedf88a8f10bb6766977cf57..9a5985ceeaa1d228cb167e60c0e6c8402533d227 100644
 --- a/browser/base/content/browser-places.js
 +++ b/browser/base/content/browser-places.js
 @@ -252,6 +252,8 @@ var StarUI = {
@@ -33,16 +33,11 @@ index 62b3665394a8256ebedf88a8f10bb6766977cf57..a0bee37cbf9e8f79b3ea69b8dec711a9
    removeBookmarkButtonCommand: function SU_removeBookmarkButtonCommand() {
      this._removeBookmarksOnPopupHidden = true;
      this.panel.hidePopup();
-@@ -1107,6 +1124,12 @@ var PlacesToolbarHelper = {
-       viewElt
-     );
- 
-+    new ZenEssentialsToolbar(
-+        `place:parent=pfgqteRgY-Wr`,
-+        document.getElementById("EssentialsToolbarItems"),
-+        document.getElementById("EssentialsToolbar")
-+    );
-+
-     if (toolbar.id == "PersonalToolbar") {
-       // We just created a new view, thus we must check again the empty toolbar
-       // message, regardless of "initialized".
+@@ -1063,6 +1080,7 @@ var PlacesToolbarHelper = {
+    * show toolbars.
+    */
+   async init() {
++    new ZenEssentialsToolbar(`place:parent=pfgqteRgY-Wr`);
+     await PlacesUIUtils.canLoadToolbarContentPromise;
+     this._realInit();
+   },