alternator: better invalid schema detection for CreateTable
alternator: better invalid schema detection for CreateTable

To be correct, CreateTable's input parsing need to work in reverse from
what it did: First, the key columns are listed in KeySchema, and then
each of these (and potetially more, e.g., from indexes) need to appear
AttributeDefinitions.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

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