feat(ui): add image viewer overlay

- Works on txt2img, canvas and workflows tabs, img2img has its own side-by-side view
- In workflow editor, the is closeable only if you are in edit mode, else it's always there
- Press `i` to open
- Press `esc` to close
- Selecting an image or changing image selection opens the viewer
- When generating, if auto-switch to new image is enabled, the viewer opens when an image comes in

To support this change, I organized and restructured some tab stuff.

invokeai/frontend/web/src/features/system/components/HotkeysModal/useHotkeyData.ts

@@ -140,6 +140,16 @@ export const useHotkeyData = (): HotkeyGroup[] => {
           desc: t('hotkeys.nextImage.desc'),
           hotkeys: [['Arrow Right']],
         },
+        {
+          title: t('hotkeys.openImageViewer.title'),
+          desc: t('hotkeys.openImageViewer.desc'),
+          hotkeys: [['I']],
+        },
+        {
+          title: t('hotkeys.backToEditor.title'),
+          desc: t('hotkeys.backToEditor.desc'),
+          hotkeys: [['Esc']],
+        },
       ],
     }),
     [t]