R1:d67cc8e5c59c

Remove some redundant information from the Ferret engine index

Summary:
Ref T12819. The "full" field has all other fields, and the "core" field has "title" and "body". Due to the way the "full" and "core" fields were being built, the "core" field also got included in the "full" field, so the "full" field has two copies of the title, two copies of the body, and then one copy of everything else.

Put only one copy of each distinct thing in each "full" and "core". Also, simplify the logic a little bit so we…