compose_box: Fix order of group pm recipient pills on focus.

Earlier when compose box was opened or narrowed to pm, the recipient
pills were sorted according to user email strings instead of their
full names which was inconsistent with compose box placeholder text,
recipient row and message header.

This commit fixes the behaviour by introducing a `sort_email`
function to sort emails according to their full names and display
sorted pills.

Fixes: zulip#27375.

Co-authored-by: richardshaju <richardshaju66@gmail.com>

web/src/drafts.ts

@@ -354,9 +354,10 @@ export function restore_message(draft: LocalStorageDraft): ComposeArguments {
     const recipient_emails = draft.private_message_recipient
         .split(",")
         .filter((email) => people.is_valid_email_for_compose(email));
+    const sorted_recipient_emails = people.sort_emails_by_username(recipient_emails);
     return {
         type: "private",
-        private_message_recipient: recipient_emails.join(","),
+        private_message_recipient: sorted_recipient_emails.join(","),
         content: draft.content,
     };
 }