types: Don't modify the type list in db::cql_type_parser::raw_builder
types: Don't modify the type list in db::cql_type_parser::raw_builder

With this patch db::cql_type_parser::raw_builder creates a local copy
of the list of existing types and uses that internally. By doing that
build() should have no observable behavior other than returning the
new types.

Signed-off-by: Rafael Ávila de Espíndola <1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>

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