Reload file metadata for truncate op in metastore

Truncate operation via HMS will generate an alter table event and the alter table event has a field 'isTruncateOp' set to true which indicates that the alter table event is generated due to truncate table operation.

After IMPALA-11534, we don't reload file metadata for every trivial alter table operation. This Jira tracks the issue to verify that file metadata is reloaded in the event processor of CatalogD when the alter table event from HMS is due to a truncate operation.