feat(core): refactor sidebar header (#6251)

- Add user avatar
- Move sign-out/user settings link from workspace-modal to user avatar modal
- Modify the style of workspace list items
- Modify gap of navigation buttons
- Animate Syncing/Offline/...

![CleanShot 2024-03-22 at 10.22.38.gif](https://graphite-user-uploaded-assets-prod.s3.amazonaws.com/LakojjjzZNf6ogjOVwKE/7305f561-a85b-4ec6-89c2-27e2f1b63c85.gif)

tests/kit/utils/sidebar.ts

@@ -12,6 +12,10 @@ export async function clickSideBarCurrentWorkspaceBanner(page: Page) {
   return page.getByTestId('current-workspace').click();
 }
 
+export async function clickSideBarUseAvatar(page: Page) {
+  return page.getByTestId('sidebar-user-avatar').click();
+}
+
 export async function clickNewPageButton(page: Page) {
   return page.getByTestId('sidebar-new-page-button').click();
 }