Replace in buffer adjustments (#2960)

This PR addresses feedback from @maxbrunsfeld on new replace in buffer.
It fixes:
- missing padding surrounding replace input.
- missing padding around replace buttons.
- missing `.notify` call which made the replace fields not show up
immediately sometimes.

Release Notes:
- N/A

---------

Co-authored-by: Max <max@zed.dev>

assets/keymaps/default.json

@@ -231,7 +231,14 @@
     }
   },
   {
-    "context": "BufferSearchBar > Editor",
+    "context": "BufferSearchBar && in_replace",
+    "bindings": {
+      "enter": "search::ReplaceNext",
+      "cmd-enter": "search::ReplaceAll"
+    }
+  },
+  {
+    "context": "BufferSearchBar && !in_replace > Editor",
     "bindings": {
       "up": "search::PreviousHistoryQuery",
       "down": "search::NextHistoryQuery"