Security Solution: Add entity threat hunting feature flag

Author: abhishekbhatia1710

x-pack/solutions/security/plugins/security_solution/common/experimental_features.ts

@@ -76,6 +76,11 @@ export const allowedExperimentalValues = Object.freeze({
    */
   entityDetailsHighlightsEnabled: false,
 
+  /**
+   * Enables the experimental Threat Hunting home experience.
+   */
+  entityThreatHuntingEnabled: false,
+
   /**
    * disables ES|QL rules
    */