Subqueries Stage 3 - Finalize design for MultiExtendedOp with order by and limit

Queries having lower level order by and limit clauses without grouping by partition key are hard to optimize. This work is to be done in the next development cycle, however, design need to be finished and agreed on it before the developmentcolor: yellow
id: 551b3377664ce8ff30d7f9d1
idBoard: 551b33775b5e1cdb5cabb3e8
name: Feature
uses: 27

No files, tests, or entry points are named. Start by locating the existing MultiExtendedOp handling and how lower-level ORDER BY and LIMIT clauses are planned for queries without the partition key. Done means the design is documented and agreed on before implementation begins.

Written by the indexing model from the issue text.