Use read-only access methods for read-only entity operations (#31254)

This PR replaces some `update()` calls with either `read()` or
`read_with()` when the `update()` call performed read-only operations on
the entity.

Many more likely exist, will follow-up with more PRs.

Release Notes:

- N/A

crates/tab_switcher/src/tab_switcher_tests.rs

@@ -326,7 +326,7 @@ async fn open_buffer(
     workspace: &Entity<Workspace>,
     cx: &mut gpui::VisualTestContext,
 ) -> Box<dyn ItemHandle> {
-    let project = workspace.update(cx, |workspace, _| workspace.project().clone());
+    let project = workspace.read_with(cx, |workspace, _| workspace.project().clone());
     let worktree_id = project.update(cx, |project, cx| {
         let worktree = project.worktrees(cx).last().expect("worktree not found");
         worktree.read(cx).id()