MDEV-34707: BUF_GET_RECOVER assertion failure on upgrade

buf_page_get_gen(): Relax the assertion once more.
The LSN may grow by invoking ibuf_upgrade(), that is,
when upgrading files where innodb_change_buffering!=none was used.
The LSN may also have been recovered from a log that needs
to be upgraded to the current format.

storage/innobase/buf/buf0buf.cc

@@ -2606,8 +2606,11 @@ buf_page_get_gen(
 	would typically be around 60000 with the default
 	innodb_undo_tablespaces=3, and less than 110000 with the maximum
 	innodb_undo_tablespaces=127. */
+	ut_d(extern bool ibuf_upgrade_was_needed;)
 	ut_ad(mode == BUF_GET_RECOVER
 	      ? recv_recovery_is_on() || log_sys.get_lsn() < 120000
+	      || log_sys.get_lsn() == recv_sys.lsn + SIZE_OF_FILE_CHECKPOINT
+	      || ibuf_upgrade_was_needed
 	      : !recv_recovery_is_on() || recv_sys.after_apply);
 	ut_ad(!mtr || mtr->is_active());
 	ut_ad(mtr || mode == BUF_PEEK_IF_IN_POOL);

storage/innobase/srv/srv0start.cc

@@ -1163,8 +1163,11 @@ static dberr_t srv_log_rebuild_if_needed()
   return srv_log_rebuild();
 }
 
+ut_d(bool ibuf_upgrade_was_needed;)
+
 ATTRIBUTE_COLD static dberr_t ibuf_log_rebuild_if_needed()
 {
+  ut_d(ibuf_upgrade_was_needed= true;)
   mysql_mutex_lock(&recv_sys.mutex);
   recv_sys.apply(true);
   mysql_mutex_unlock(&recv_sys.mutex);