cql3: Implement term::to_expression for tuples
cql3: Implement term::to_expression for tuples

Each tuples::delayed_value can now be converted to expression.

Signed-off-by: Jan Ciolek <b66a6f3989e26cb552db14b7ab163c3a50292e24@scylladb.com>

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