feat(ui): revise image viewer

- Viewer only exists on Generation tab
- Viewer defaults to open
- When clicking the Control Layers tab on the left panel, close the viewer (i.e. open the CL editor)
- Do not switch to editor when adding layers (this is handled by clicking the Control Layers tab)
- Do not open viewer when single-clicking images in gallery
- _Do_ open viewer when _double_-clicking images in gallery
- Do not change viewer state when switching between app tabs (this no longer makes sense; the viewer only exists on generation tab)
- Change the button to a drop down menu that states what you are currently doing, e.g. Viewing vs Editing

invokeai/frontend/web/src/features/controlLayers/components/ControlLayersToolbar.tsx

@@ -4,7 +4,7 @@ import { BrushSize } from 'features/controlLayers/components/BrushSize';
 import ControlLayersSettingsPopover from 'features/controlLayers/components/ControlLayersSettingsPopover';
 import { ToolChooser } from 'features/controlLayers/components/ToolChooser';
 import { UndoRedoButtonGroup } from 'features/controlLayers/components/UndoRedoButtonGroup';
-import { ViewerButton } from 'features/gallery/components/ImageViewer/ViewerButton';
+import { ViewerToggleMenu } from 'features/gallery/components/ImageViewer/ViewerToggleMenu';
 import { memo } from 'react';
 
 export const ControlLayersToolbar = memo(() => {
@@ -21,7 +21,7 @@ export const ControlLayersToolbar = memo(() => {
       </Flex>
       <Flex flex={1} justifyContent="center">
         <Flex gap={2} marginInlineStart="auto">
-          <ViewerButton />
+          <ViewerToggleMenu />
         </Flex>
       </Flex>
     </Flex>