Update EventCreator to publish to the ASB registration queue

[martivj]

Description

EventCreator currently publishes new events to the Storage account's "event registration" queue. Update it to publish to the ASB registration queue instead, matching the API's own cutover for that queue.

Acceptance Criteria

• EventCreator publishes to the ASB "event registration" queue.
• Legacy Storage Queue publishing path removed from the tool (no dual-write needed here — this is a dev/test tool, not a production drain scenario).
• Relevant automated tests added or updated.