HHH-10563: Significant String use/duplication associated with subselect fetch

The use of @Fetch(FetchMode.SUBSELECT) results in a significant level of string duplication for SQL and SQL fragments. When loading large datasets and/or higher numbers of associations with multiple associations using SUBSELECT the memory can accumulate significantly (e.g. on the order of multiple GB for string space associated with the duplicate SQL fragments alone).