Ensure project search actions are always aligned (#20353)

Follow up to https://github.com/zed-industries/zed/pull/20242

This PR ensures all the actions to the right of the project search
inputs have the same minimum width, ensuring that the inputs themselves
are always aligned. In the previous PR, I didn't considered the scenario
where the project search numbers where beyond 4 or 5 digits, which then
increased their width. This should be treated now!

<img width="700" alt="Screenshot 2024-11-07 at 09 55 11"
src="https://github.com/user-attachments/assets/7a9d8ebd-b575-4141-9242-3044f00150c5">

Release Notes:

- N/A

crates/ui/src/components/icon.rs

@@ -192,6 +192,7 @@ pub enum IconName {
     FileGit,
     FileLock,
     FileRust,
+    FileSearch,
     FileText,
     FileToml,
     FileTree,