Feature/explicit duration list

[philomory]

This attempts to address #110 in a slightly more thorough way, allowing users who wish to exceed 48 hours as their max duration to do so by specifying an explicit list of values to supply in the drop down; it also has the side effect of allowing people who are fine with 48 hours or less to trim their list by omitting some of the increments.

Example usage:

module "aws_sso_elevator {
  source  = "fivexl/sso-elevator/aws"
  version = "3.0.0"

  ...
  permission_duration_list_override = ["00:30","01:00","02:00","03:00","06:00","12:00","24:00","48:00","72:00","96:00"]
  ... 
}

Resulting display:

I think it might have been even nicer to allow specifying times with e.g. "1h30m", but, this method was simpler to integrate into the existing code.