audit_events.md, integrity.md: major refactoring 3

• audit_events.md: fixup formal requirements checklist
• audit_events.md: create_db
• audit_events.md: create_local_db, drop_local_db
• integrity.md: major refactoring
• audit_events.md: integrity_violation placeholder

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• Part of #209 (closed)
• Follow-up for !361 (merged), !364 (merged)
• See also https://git.picodata.io/picodata/picodata/picodata/-/issues/340
• Target branch: main
• Changes should be cherry-picked to 24.2: yes
• Staging: https://docs.binary.picodata.io/picodata/rosik_audit_events/