fix: autoscaler asg subnets and add possibility to enable metrics for asg

[mmoutama09]

Description

Add the possibility to have multiple subnets for runner manager instance with docker-autoscaler runner type.
Add the variable enabled_metrics for docker autoscaler autoscaling group

Migrations required

No

Verification

Tested on our side on a production runner.
To enable metrics for docker autoscaler autoscaling group you have to pass a list of metrics, here is my conf

runner_worker_docker_autoscaler_asg = {
         ...
         enabled_metrics  = ["GroupMinSize",  "GroupMaxSize", "GroupInServiceInstances", "GroupPendingInstances", 
                                         "GroupStandbyInstances", "GroupTerminatingInstances", "GroupTotalInstances"]

[github-actions]

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[kayman-mk]

Looks good to me. Thanks!

Could you please add a description to the PR and also describe how you tested the change?