This should allow specifying ‘wildcardProjection’ when creating a compound wildcard index, which includes:

1. validating the ‘wildcardProjection’ option (e.g. wildcardProjection should only ever be specified if the wildcard field is “$**” and should exclude all overlapping fields)

2. Extend support in which cases ‘wildcardProjection’ is used:

    a) The Index indexability/discriminators encoding for Plan cache keys 

    b) Planner params fill-out process.