[Security Solution] Implement prebuilt rule upgrade/_review API endpoint

[banderror]

Epic: https://github.com/elastic/security-team/issues/1974 (internal)
Related to: #144060, #148181

Summary

Based on the API design made in #144060, implement the new rule upgrade/_review API endpoint and hide it behind the feature flag. See the draft implementation in the POC.

POST /internal/detection_engine/prebuilt_rules/upgrade/_review

Response body:

export interface ReviewRuleUpgradeResponseBody {
  status_code: number;
  message: string;
  attributes: {
    /** Aggregated info about all rules available for upgrade */
    stats: RuleUpgradeStatsForReview;
    /** Info about individual rules: one object per each rule available for upgrade */
    rules: RuleUpgradeInfoForReview[];
  };
}

export interface RuleUpgradeStatsForReview {
  /** Number of installed prebuilt rules available for upgrade (stock + customized) */
  num_rules_to_upgrade: number;
  /** Number of installed prebuilt rules available for upgrade which are stock (non-customized) */
  num_stock_rules_to_upgrade: number;
  /** Number of installed prebuilt rules available for upgrade which are customized by the user */
  num_customized_rules_to_upgrade: number;
  /** A union of all tags of all rules available for upgrade */
  tags: RuleTagArray;
  /** A union of all fields "to be upgraded" across all the rules available for upgrade. An array of field names. */
  fields: string[];
}

export interface RuleUpgradeInfoForReview {
  id: RuleObjectId;
  rule_id: RuleSignatureId;
  rule: DiffableRule;
  diff: {
    fields: {
      name?: ThreeWayDiff<RuleName>;
      description?: ThreeWayDiff<RuleDescription>;
      // etc; only fields that have some changes or conflicts will be returned
    };
    has_conflict: boolean;
  };
}

Todo

• Initial implementation (PR)
• Implement RuleUpgradeStatsForReview.tags

[elasticmachine]

Pinging @elastic/security-detections-response (Team:Detections and Resp)

[elasticmachine]

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