Handle AWS ELB target group names > 32 characters

[johananl]

ELB target groups are limited to 32 characters on the AWS API. Since we interpolate the cluster name and worker pool name into the target group, long cluster/pool names may exceed this limit.

At the moment there is no check in place for this limit - we fail the deployment with a not-so-nice Terraform error. Ideally we should find a way to never hit this limit. An alternative would be to validate the config and fail fast if necessary.

[johananl]

Handled in #367. We simply let Terraform generate a random target group name and put the meaningful info (cluster + worker pool name) in AWS tags.

[invidian]

See also #282.

[johananl]

#367 is merged. Closing.