test: Fix flaky `workflow_id` parse in playbooks test

[topher-lo]

What changed

• Ignore secrets creation fixture errors (to deal with local development case when secrets have already been created and clash)
• Replaced create workflows CLI commands in test with direct calls to the REST API via the private create and activate workflow functions
• That function returns a json with workflow ID under the id field
• Replaced inputs with triggers in AWS guardduty to slack playbook