Add join size to the exec detail of join executors

## Enhancement
To support the plan based RU, the join executors should expose the join size to the exec detail. So the later RU calculation can read the information.

Start by locating the join executor implementations and the code that builds their exec detail. Check how existing executor statistics are exposed and identify the join-size value needed by later RU calculation. Done means join executors expose join size in exec detail for that calculation.

Written by the indexing model from the issue text.