Move AutoScalingGroupClient from autoscaling_groups_client.go to autoscaling_groups.go

[ShubhamPalriwala]

Describe the bug
We right now define a type interface AutoScalingGroupClient in a file and no other use case is there, it would be a cleaner approach to move it to the core autoscaling_groups.go file for easier code readability.

Additional context

• Original file from where the type is to be moved:
  https://github.com/tailwarden/komiser/blob/develop/providers/aws/ec2/autoscaling_groups_client.go

• File the type should be moved to:
  https://github.com/tailwarden/komiser/blob/develop/providers/aws/ec2/autoscaling_groups.go

[alexandreliberato]

I can work on this.

[ShubhamPalriwala]

thanks @alexandreliberato, since you commented first, i'm assigning this to you!