Add an option to configure preferred AWS availability zones for cluster creation

[binlab]

For now, the count of subnets calculated dynamically using as an input data resource data.aws_availability_zones. For some regions (e.g. us-east-1 with has 6 availability zones for now) and some small clusters (e.g. 3 nodes), some subnets might be redundant. In addition, it is not possible to specify preferred availability zones for cluster creation. It would be nice to have the option to provide a list of desired availability zones.

[Narragansett]

I changed main.tf to this as the list of preferred availability zones. Is this what you asked for?
data "aws_availability_zones" "current" {
filter {
name = "zone-name"
values = ["us-east-1a","us-east-1b","us-east-1c","us-east-1d","us-east-1f"]
}
}

[binlab]

@Narragansett thank you for the suggestion! Yes, this solution might fit. But in this case, may need to be more strictly limited than filter