view: add handling of a token column for secondary indexes
view: add handling of a token column for secondary indexes

In order to ensure token order on secondary index queries,
first clustering column for each view that backs a secondary index
is going to store a token computed from base's partition keys.
After this commit, if there exists a column that is not present
in base schema, it will be filled with computed token.

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