Dynamic Index Build Side is Statically Chosen

## Expected behavior
During dynamic join queries on commutative conditions, the local index is built on whichever side is smaller, and the other side is streamed against it. This likely requires some linear scans prior to running

## Actual behavior
We must specify the side on which to build the index for all partitions apriori when using ```JoinQueries.SpatialJoinQueryFlat```.

## Steps to reproduce the problem
N/A

## Settings
N/A

Start by reading JoinQueries.SpatialJoinQueryFlat and trace how the index-building side is selected for dynamic joins on commutative conditions. The work is done when each partition can build its local index on the smaller side and stream the other side against it, including any required scans before execution.

Written by the indexing model from the issue text.