Improve default allocation size in N1QL projection

The projection operator allocates extra memory to minimize resizing maps. This is causing excessive memory usage in some situations.

Per Sitaram Vemulapalli:

A customer reported high memory usage of query node. They use * and One of the place is below.
Are we need to add +32 for ‘*’ also? Is there way we can calculate the right number form projection?
Looks like n is 1 and 8.23GB around 30 * 297MB

https://github.com/couchbase/query/blob/master/execution/project_initial.go#L100

297.01MB   297.01MB     97:sv := value.NewScopeValue(make(map[string]interface{}, n), item)

         .      111MB     98:pv := value.NewAnnotatedValue(sv)

         .          .     99:pv.SetAnnotations(item)

         .          .    100:

    8.23GB     8.23GB    101:p := value.NewValue(make(map[string]interface{}, n+32))