refactor(core): workbench (#7355)

Merge the right sidebar logic into the workbench. this can simplify our logic.

Previously we had 3 modules

* workbench
* right-sidebar (Control sidebar open&close)
* multi-tab-sidebar (Control tabs)

Now everything is managed in Workbench.

# Behavioral changes

The sidebar button is always visible and can be opened at any time.
If there is no content to display,  will be `No Selection`

![CleanShot 2024-06-28 at 14.00.41.png](https://graphite-user-uploaded-assets-prod.s3.amazonaws.com/g3jz87HxbjOJpXV3FPT7/d74b3a60-2299-452e-877e-188186fe5ee5.png)

Elements in the sidebar can now be defined as`unmountOnInactive=false`. Inactive sidebars are marked with `display: none` but not unmount, so the `ChatPanel` can always remain in the DOM and user input will be retained even if the sidebar is closed.

packages/frontend/component/src/components/resize-panel/resize-panel.tsx

@@ -39,6 +39,7 @@ export interface ResizePanelProps
   resizeHandleVerticalPadding?: number;
   enableAnimation?: boolean;
   width: number;
+  unmountOnExit?: boolean;
   onOpen: (open: boolean) => void;
   onResizing: (resizing: boolean) => void;
   onWidthChange: (width: number) => void;
@@ -149,6 +150,7 @@ export const ResizePanel = forwardRef<HTMLDivElement, ResizePanelProps>(
       floating,
       enableAnimation: _enableAnimation = true,
       open,
+      unmountOnExit,
       onOpen,
       onResizing,
       onWidthChange,
@@ -182,7 +184,7 @@ export const ResizePanel = forwardRef<HTMLDivElement, ResizePanelProps>(
         data-handle-position={resizeHandlePos}
         data-enable-animation={enableAnimation && !resizing}
       >
-        {status !== 'exited' && children}
+        {!(status === 'exited' && unmountOnExit !== false) && children}
         <ResizeHandle
           resizeHandlePos={resizeHandlePos}
           resizeHandleOffset={resizeHandleOffset}