agent: Refresh the profile selector and modal design (#29816)

- [x] Separate MCP servers from tools in the profile customization modal
view
- [x] Group MCP tools in the MCP picker and add a heading
- [x] Separate bult-in profiles from custom ones in the dropdown
selector
- [x] Separate bult-in profiles from custom ones in the modal
- [ ] Enable looping through items via keybinding without opening the
dropdown (will be done on a follow-up PR)
- [ ] Stretch: Focus on the currently active item upon opening the
dropdown (will be done on a follow-up PR)

Release Notes:

- N/A

---------

Co-authored-by: Bennet Bo Fenner <53836821+bennetbo@users.noreply.github.com>
Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>
Co-authored-by: Bennet Bo Fenner <bennet@zed.dev>

crates/icons/src/icons.rs

@@ -158,6 +158,7 @@ pub enum IconName {
     Maximize,
     Menu,
     MenuAlt,
+    MessageBubbleDashed,
     MessageBubbles,
     Mic,
     MicMute,
@@ -194,6 +195,7 @@ pub enum IconName {
     RotateCw,
     Route,
     Save,
+    Scissors,
     Screen,
     SearchCode,
     SearchSelection,