Add hash table size into exec detail

## Enhancement
To support plan based RU, this critical information should be exposed to the exec detail of agg and join

Start by locating the exec detail generation for aggregation and join operators, then trace where hash table information is available during execution. Check how plan-based RU consumes exec detail and define done as exposing hash table size for both operator types in the resulting details.

Written by the indexing model from the issue text.