[DE][Custom Highlighted Fields] - follow up work required

[yctercero]

Working through a PR to allow users to add custom highlighted fields defined on the rule schema - https://github.com/elastic/kibana/pull/163235

• [ ] Fix and unskip https://github.com/elastic/kibana/blob/main/x-pack/test/security_solution_cypress/cypress/e2e/exceptions/alerts_table_flow/rule_exceptions/closing_all_matching_alerts.cy.ts
• [ ] Fix and unskip https://github.com/elastic/kibana/blob/main/x-pack/test/security_solution_cypress/cypress/e2e/exceptions/alerts_table_flow/rule_exceptions/auto_populate_with_alert_data.cy.ts
• [x] Update schema to be an object rather than string[]
  • Georgii made the argument that using an object would be better so that if we add more features, like allowing the user to specify if they want their selected fields to override ours or be additive, then we would just add a param to the object.
  • Something like:

{
  "investigation_fields": {
    "fields": [],
    "override": false,
  }
}

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[yctercero]

Closing - out of date.