Note: This tickets depends on the design review for cost-based plan ranker. Please refer to CBR design doc

This ticket includes a sequence of sub-tasks:

1. SERVER-95088 Re-use the tests from existing histogram CE and copy them to cbp_histogram_ce
2. SERVER-95249 Rename test_helpers to test_utils
3. SERVER-95089 Delete the remaining Bonsai code in CE
4. SERVER-95090 Move files from cbp_histogram_ce folder to ce folder (make a flat file organization)
5. SERVER-95091 Update the C++ namespace from mongo::optimizer::ce::cbp to mongo::ce
6. SERVER-95092 Rename histogram_predicate_estimation.h/.cpp files to histogram_estimator.h/.cpp
7. SERVER-95179 Merge array_histogram_helpers.h/.cpp and scalar_histogram_helpers.h/.cpp
8. SERVER-95180 Clean the includes and libraries included in compiling the code of histogram CE