SERVER-116135 enabled SBE to use sparse B-tree/hashed foreign indexes in $lookup via the dynamic indexed loop join (DILJ). Wildcard indexes that cover the foreign field were explicitly kept classic-only and left as a follow-up.

Supporting wildcard indexes requires making them eligible for SBE pushdown, ensuring they always route through DILJ (since they omit documents where the indexed field is missing, similar to sparse indexes), and correctly handling the virtual key structure wildcard indexes use when performing index seeks in SBE.

Related: SERVER-116135 (sparse indexes in SBE $lookup), SERVER-64082 (original classic-only gate)