Remove segment_names field from Replay responses; add webhookEvents to SentryApp

This diff makes two distinct changes:

• segment_names removed: The segment_names field (nullable array of strings) is removed from Replay response schemas across multiple endpoints, and segment_names is also removed from the valid enum values for the field query parameter. Clients requesting segment_names as a field or reading it from replay responses will break.
• webhookEvents added: A new webhookEvents field (array of strings, e.g. issue.assigned, issue.created, etc.) is added to SentryApp response schemas and marked as required in the required array. This is a new response field that existing integrations can now read, but its addition to required means schema validators may flag existing responses that omit it.