Add enterprise structured content chunker
Just a small class that parses, flatten and trim the structured content docs. It's not connected to anything yet but seemed isolated enough from the rest that a dedicated commit could make sense. The trimming strategy is taken from early expiriment where the following criteria were applied:
- max passage length: 2800
- min passage length: 40
- max list size: 10
- max number of passage: 150
Bug: T414070