perf(import): optimize search for domains claimed by other organizations (#8200)

# Which Problems Are Solved

Improve the performance of human imports by optimizing the query that
finds domains claimed by other organizations.

# How the Problems Are Solved

Use the fields search table introduced in
https://github.com/zitadel/zitadel/pull/8191 by storing each
organization domain as Object ID and the verified status as field value.

# Additional Changes

- Feature flag for this optimization

# Additional Context

- Performance improvements for import are evaluated and acted upon
internally at the moment

---------

Co-authored-by: adlerhurst <silvan.reusser@gmail.com>

internal/api/grpc/feature/v2/converter.go

@@ -115,6 +115,8 @@ func improvedPerformanceTypeToPb(typ feature.ImprovedPerformanceType) feature_pb
 		return feature_pb.ImprovedPerformance_IMPROVED_PERFORMANCE_PROJECT
 	case feature.ImprovedPerformanceTypeUserGrant:
 		return feature_pb.ImprovedPerformance_IMPROVED_PERFORMANCE_USER_GRANT
+	case feature.ImprovedPerformanceTypeOrgDomainVerified:
+		return feature_pb.ImprovedPerformance_IMPROVED_PERFORMANCE_ORG_DOMAIN_VERIFIED
 	default:
 		return feature_pb.ImprovedPerformance(typ)
 	}
@@ -145,6 +147,8 @@ func improvedPerformanceToDomain(typ feature_pb.ImprovedPerformance) feature.Imp
 		return feature.ImprovedPerformanceTypeProject
 	case feature_pb.ImprovedPerformance_IMPROVED_PERFORMANCE_USER_GRANT:
 		return feature.ImprovedPerformanceTypeUserGrant
+	case feature_pb.ImprovedPerformance_IMPROVED_PERFORMANCE_ORG_DOMAIN_VERIFIED:
+		return feature.ImprovedPerformanceTypeOrgDomainVerified
 	default:
 		return feature.ImprovedPerformanceTypeUnknown
 	}