Adjust spacing and sizing of buffer search bar icon buttons (#18638)

This PR mostly makes all of the search bar icon buttons all squared and
adjusts the spacing between them, as well as the additional input that
appears when you toggle the "Replace all" action.

<img width="900" alt="Screenshot 2024-10-02 at 6 08 30 PM"
src="https://github.com/user-attachments/assets/86d50a3b-94bd-4c6a-822e-5f7f7b2e2707">

---

Release Notes:

- N/A

crates/search/src/project_search.rs

@@ -1634,7 +1634,7 @@ impl Render for ProjectSearchBar {
                             let focus_handle = focus_handle.clone();
                             move |cx| {
                                 Tooltip::for_action_in(
-                                    "Toggle replace",
+                                    "Toggle Replace",
                                     &ToggleReplace,
                                     &focus_handle,
                                     cx,