In order to support the production CBR mode where multi-planning (MP) is used first, and eventually may fallback to CBR, the currently existing "automaticCE" query knob will be used for this production mode, while the current functionality of "automaticCE" will be supported by a new knob "histogramCEwithHeuristicFallback".

Based on a discussion with philip.stoev@mongodb.com this change also entails the following test-related changes:

Approximately the following:

• a new passthrough for automaticHistogramCE
• move the existing expected file from automaticCE to automaticHisogramCE, and modify it slightly because the expected file contains the name of the CBR mode in it
• record a new expected file for the new automaticCE
• fish for regressions between the new automaticCE and multiPlanning