zeta: Add adjustments to the review modal UI (#21920)

Most notably, adding a current iteration of a possible logo to feel it
out! :) Also, I'm hiding the input and instructions container after the
review has been sent. In the future, if we allow changing an already
sent review, we can change this behavior.

<img width="800" alt="Screenshot 2024-12-12 at 10 42 44"
src="https://github.com/user-attachments/assets/37e63d0d-d847-445e-bdf8-bf5c97d0fe4c"
/>

Release Notes:

- N/A

crates/ui/src/components/icon.rs

@@ -303,6 +303,7 @@ pub enum IconName {
     XCircle,
     ZedAssistant,
     ZedAssistantFilled,
+    ZedPredict,
     ZedXCopilot,
 }