Progress doc: https://docs.google.com/document/d/1EJ_7MbJPsnFJo9v_T5afrCYgmJuMsxdLN5nz5KwK_js/edit 

We have 2 feature branches – pm3660-histogram and SPM-3182. 

pm3660-histogram

The feature branch https://github.com/10gen/mongo/compare/master...pm3660-histogram . We have 5 commits on this branch now.

1. SERVER-91607: Create mock interface for histogram CE
2. SERVER-91636 validating cardinality estimation for equality predicate
3. SERVER-86748 Fix maxdiff to sort on difference in area between buckets
4. SERVER-92027 Add unit tests for estimateCardinality inequality compar…
5. SERVER-91638 Implement cardinality estimation unit tests for range in…

We need to come up a strategy to merge them to master. A few known problems to address:

1. The very first commit introduces a error (duplicate errorcode) and that is addressed in later commit
2. Bonsai code is fully removed at this moment. We need to break that dependency at the front of the queue.

SPM-3182

There are 8 commits. Some of them have merge conflicts to resolve.