How do I reference launch template version number in auto scaling group?

How do I add a reference to the latest version number of the launch template in the auto-scaling group? The launch template and auto scaling group are in separate files as the launch template is used by other autoscaling groups as well. Can Fn::GetAtt and Ref be used here to refer to another resource located in a separate file? If so, how can I use it? The end goal is when I make an update to the launch template, the autoscaling group should automatically refer to the latest launch template.

Note - I am creating the launch template completely separate before creating the auto-scaling group. It works this way, but I would like the auto-scaling group to refer to the latest launch template. It currently defaults to version 1.

launch_template.yaml

---
AWSTemplateFormatVersion: '2010-09-09'
Resources:
  LaunchTemplate:
    Type: 'AWS::EC2::LaunchTemplate'
    Properties:
      LaunchTemplateName: testtemplate
      LaunchTemplateData:
        IamInstanceProfile:
          Arn: >-
            arn:aws:iam::blah
        ImageId: ami-12345
        InstanceRequirements:
          InstanceGenerations:
            - current
          MemoryMiB:
            Min: 8192
          VCpuCount:
            Min: 2
            Max: 4
        BlockDeviceMappings:
          - Ebs:
              VolumeSize: 16
              VolumeType: gp2
              DeleteOnTermination: true
              Encrypted: true
            DeviceName: /dev/xvda
        Monitoring:
          Enabled: true
        KeyName: testkey
        SecurityGroupIds:
          - sg-1234
        PrivateDnsNameOptions:
          HostnameType: ip-name
        InstanceInitiatedShutdownBehavior: terminate

autoscaling_group.yaml

---
Resources:
  testautoscalinggroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      AutoScalingGroupName: test-autoscaling-group
      MaxSize: '2'
      MinSize: '1'
      DesiredCapacity: '1'
      VPCZoneIdentifier:
        - subnet-1234
      TargetGroupARNs: 
        - Ref: targetgroup
      MixedInstancesPolicy:
        InstancesDistribution:
          OnDemandAllocationStrategy: lowest-price
        LaunchTemplate:
          LaunchTemplateSpecification:
            LaunchTemplateName: testtemplate
      Tags:
        - Key: Cluster
          Value: test
          PropagateAtLaunch: true
  dynamicscalingpolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      AutoScalingGroupName:
        Ref: testautoscalinggroup
      PolicyType: TargetTrackingScaling
      TargetTrackingConfiguration:
        DisableScaleIn: false
        PredefinedMetricSpecification:
          PredefinedMetricType: ASGAverageCPUUtilization
        TargetValue: 30
  targetgroup:
    Type: 'AWS::ElasticLoadBalancingV2::TargetGroup'
    Properties:
      HealthCheckEnabled: true
      HealthCheckIntervalSeconds: 30
      HealthCheckProtocol: TCP
      HealthCheckTimeoutSeconds: 10
      HealthyThresholdCount: 3
      Name: testtargetgroup
      Protocol: TCP_UDP
      Port: 53
      UnhealthyThresholdCount: 3
      VpcId: vpc-1234