ECS audit events for alerts plugin

[thomheymann]

In order to support better auditing capabilities across the stack we would like to add ECS audit events to alerts plugin:

• Remove legacy audit events in alerts plugin:

  • alerts_authorization_failure
  • alerts_authorization_success
  • actions_authorization_failure
  • actions_authorization_success

• Following auditing guidelines, create ECS audit events using the new audit service API:

  const auditLogger = securitySetup.audit.withRequest(request);
  auditLogger.log({
    message: 'User is updating dashboard [id=123]',
    event: {
      action: 'saved_object_update',
      outcome: 'unknown',
    },
    kibana: {
      saved_object: { type: 'dashboard', id: '123' },
    },
  });

Event types: https://docs.google.com/document/d/1J4iv3WhkfJqH241KmBPW6eOZGe4MbBz6XE_KlBL2-_s/edit#

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)

[thomheymann]

Requires #42762 so that we can generate the correct id when logging a create event before actually creating an alert / action