feat: support setting throughput and iops for ebs volumes (#1063)

## Description

These changes will add support for setting `throughput` and `iops` to
the EBS device that is being attached to the docker_machine instance.
Because setting `iops` is now possible, this will also allow the usage
of `io1` and `io2` EBS volumes types.

## Migrations required

No - If you consider my defaults for the two new variables as sane.

## Verification

I have adapted the module configuration by changing the
`runner_worker_docker_machine_instance` input variables:

```
  runner_worker_docker_machine_instance = {
    private_address_only = false
    types                = ["m5.large", "t3.xlarge", "m6a.large"]
    subnet_ids           = [module.vpc.public_subnets[0]]
    runners_idle_time    = 180
    root_size            = 30
    volume_type          = "io2"
    volume_iops          = 6000
  }
```

The volume was created successfully when testing the runner via Gitlab:

<img width="1144" alt="Screenshot 2024-01-06 at 12 14 09"
src="https://github.com/cattle-ops/terraform-aws-gitlab-runner/assets/25439373/0beca11e-78fd-4ac7-ae9d-47df3c5c1a9f">

Author: tibuntu

main.tf

@@ -330,6 +330,8 @@ resource "aws_launch_template" "fleet_gitlab_runner" {
     ebs {
       volume_size = var.runner_worker_docker_machine_instance.root_size
       volume_type = var.runner_worker_docker_machine_instance.volume_type
+      iops        = contains(["gp3", "io1", "io2"], var.runner_worker_docker_machine_instance.volume_type) ? var.runner_worker_docker_machine_instance.volume_iops : null
+      throughput  = var.runner_worker_docker_machine_instance.volume_type == "gp3" ? var.runner_worker_docker_machine_instance.volume_throughput : null
     }
   }
 

variables.tf

@@ -666,7 +666,9 @@ variable "runner_worker_docker_machine_instance" {
     start_script = Cloud-init user data that will be passed to the Runner Worker. Should not be base64 encrypted.
     subnet_ids = The list of subnet IDs to use for the Runner Worker when the fleet mode is enabled.
     types = The type of instance to use for the Runner Worker. In case of fleet mode, multiple instance types are supported.
-    volume_type = The type of volume to use for the Runner Worker.
+    volume_type = The type of volume to use for the Runner Worker. `gp2`, `gp3`, `io1` or `io2` are supported.
+    volume_throughput = Throughput in MB/s for the volume. Only supported when using `gp3` as `volume_type`.
+    volume_iops = Guaranteed IOPS for the volume. Only supported when using `gp3`, `io1` or `io2` as `volume_type`.
   EOT
   type = object({
     destroy_after_max_builds   = optional(number, 0)
@@ -683,6 +685,8 @@ variable "runner_worker_docker_machine_instance" {
     subnet_ids                 = optional(list(string), [])
     types                      = optional(list(string), ["m5.large"])
     volume_type                = optional(string, "gp2")
+    volume_throughput          = optional(number, 125)
+    volume_iops                = optional(number, 3000)
   })
   default = {
   }
@@ -696,6 +700,11 @@ variable "runner_worker_docker_machine_instance" {
     condition     = var.runner_worker_docker_machine_instance.name_prefix == "" || can(regex("^[a-zA-Z0-9\\.-]+$", var.runner_worker_docker_machine_instance.name_prefix))
     error_message = "Valid characters for the docker+machine executor name are: [a-zA-Z0-9\\.-]."
   }
+
+  validation {
+    condition     = contains(["gp2", "gp3", "io1", "io2"], var.runner_worker_docker_machine_instance.volume_type)
+    error_message = "Supported volume types: gp2, gp3, io1 and io2"
+  }
 }
 
 variable "runner_worker_docker_machine_instance_spot" {