Review CREATE STREAM and CREATE MATERIALIZED VIEW syntax

[jfallows]

Describe the desired outcome from the user's perspective
As appdev, I want to create request-response APIs via zillabase simply in SQL.

Acceptance criteria

• Map as closely as possible to existing concepts
• Minimize introduction of zilla-specific nuances if possible

Additional context
Consider syntax such as CREATE CHANNEL ... and CREATE CHANNEL ... WITH ( reply_to= ... } etc.
Consider how to also support CREATE TABLE ... without implicitly triggering source and sync to Kafka.