feat: Remove "jobs" from imap_markseen if folder doesn't exist (#5870)

Add a `create` param to `select_with_uidvalidity()` instead of always trying to create the folder
and return `Ok(false)` from it if the folder doesn't exist and shouldn't be created, and handle this
in `store_seen_flags_on_imap()` by just removing "jobs" from the `imap_markseen` table. Also don't
create the folder in other code paths where it's not necessary.

src/imap/idle.rs

@@ -29,7 +29,9 @@ impl Session {
     ) -> Result<Self> {
         use futures::future::FutureExt;
 
-        self.select_with_uidvalidity(context, folder).await?;
+        let create = true;
+        self.select_with_uidvalidity(context, folder, create)
+            .await?;
 
         if self.drain_unsolicited_responses(context)? {
             self.new_mail = true;