22fa00152

This PR is for Summer-2022 Implement the Low Cardinality HashMap project, and the project ID is 22fa00152.
This PR is implementing a low cardinality index, and will use it to optimize JOIN and GROUP BY.

The design documentation has been uploaded to https://github.com/matrixorigin/docs/blob/main/design/low_cardinality_design_doc.md



Co-authored-by: bRong Njam <longran1989@gmail.com>