cql3: expression: evaluate() support subscripting lists
cql3: expression: evaluate() support subscripting lists

We already support subscripting maps (for filtering WHERE m[3] = 6),
so adding list subscript support is easy. Most of the code is shared.
Differences are:
 - internal list representation is a vector of values, not of key/values
 - key type is int32_type, not defined by map
 - need to check index bounds

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla