Improve project search design details (#22529)

Closes https://github.com/zed-industries/zed/issues/22469 — and, aside
from fixing that issue also took the opportunity to make the
`file_search` icon dimensions feel better in comparison the other icons
in the Project Search area.

Release Notes:

- N/A

assets/icons/file_search.svg

@@ -1 +1,5 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="lucide lucide-file-search"><path d="M14 2v4a2 2 0 0 0 2 2h4"/><path d="M4.268 21a2 2 0 0 0 1.727 1H18a2 2 0 0 0 2-2V7l-5-5H6a2 2 0 0 0-2 2v3"/><path d="m9 18-1.5-1.5"/><circle cx="5" cy="14" r="3"/></svg>
+<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M5.2345 20.1C5.38772 20.373 5.60794 20.5998 5.87313 20.7577C6.13832 20.9157 6.43919 20.9992 6.74562 21H17.25C17.7141 21 18.1592 20.8104 18.4874 20.4728C18.8156 20.1352 19 19.6774 19 19.2V7.5L14.625 3H6.75C6.28587 3 5.84075 3.18964 5.51256 3.52721C5.18437 3.86477 5 4.32261 5 4.8V6.5" stroke="black" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M10 16.8182L8.5 15.3182" stroke="black" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M6 15.8182C7.65685 15.8182 9 14.475 9 12.8182C9 11.1613 7.65685 9.81818 6 9.81818C4.34315 9.81818 3 11.1613 3 12.8182C3 14.475 4.34315 15.8182 6 15.8182Z" stroke="black" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>