Better messaging for accounts that are too young (#31212)

Right now you find this out the first time you try and submit a
completion.

These changes communicate much earlier to the user what the issue is
with their account and what they can do about it.

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>

crates/zeta/src/zeta.rs

@@ -1574,6 +1574,16 @@ impl inline_completion::EditPredictionProvider for ZetaInlineCompletionProvider
             return;
         }
 
+        if self
+            .zeta
+            .read(cx)
+            .user_store
+            .read(cx)
+            .current_user_account_too_young()
+        {
+            return;
+        }
+
         if let Some(current_completion) = self.current_completion.as_ref() {
             let snapshot = buffer.read(cx).snapshot();
             if current_completion