feat: message info: add database msg ID

We have recently removed it from the normal "message info" dialog
at least on Delta Chat Desktop, so without this one can't easily find
the ID of a particular message,
which is useful for debugging.

src/message.rs

@@ -324,6 +324,7 @@ SELECT ?1, rfc724_mid, pre_rfc724_mid, timestamp, ?, ? FROM msgs WHERE id=?1
         if duration != 0 {
             ret += &format!("Duration: {duration} ms\n",);
         }
+        ret += &format!("\nDatabase ID: {}", msg.id);
         if !msg.rfc724_mid.is_empty() {
             ret += &format!("\nMessage-ID: {}", msg.rfc724_mid);