feat: Add availability_zone output

[deny-7]

Description

Added availability_zone output. The availability_zone of the created instance is useful information to use outside of the module.

Motivation and Context

When creating multiple EC2 instances in multiple AZs, in most cases, we would like to have the EBS volume in the same AZ as the created EC2. As a trick we can use data.aws_instance with loop or a map of AZs and random_suffle,
but it does not look nice. In my opinion having availability_zone output would get out of tricks and make the code cleaner and easier to read.

This PR resolves #341 and #264

Breaking Changes

None

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects
  Deployed volume-attachment example:

terraform plan --target module.ec2 --target aws_volume_attachment.this --target aws_ebs_volume.this

  # aws_ebs_volume.this will be created
  + resource "aws_ebs_volume" "this" {
      + arn               = (known after apply)
      + availability_zone = "eu-west-1c"
      + encrypted         = (known after apply)
      + final_snapshot    = false
      + id                = (known after apply)
      + iops              = (known after apply)
      + kms_key_id        = (known after apply)
      + size              = 1
      + snapshot_id       = (known after apply)
      + tags              = {
          + "Example"    = "ex-volume-attachment"
          + "Name"       = "ex-volume-attachment"
          + "Repository" = "https://github.com/terraform-aws-modules/terraform-aws-ec2-instance"
        }
      + tags_all          = {
          + "Example"    = "ex-volume-attachment"
          + "Name"       = "ex-volume-attachment"
          + "Repository" = "https://github.com/terraform-aws-modules/terraform-aws-ec2-instance"
        }
      + throughput        = (known after apply)
      + type              = (known after apply)
    }

  # aws_volume_attachment.this will be created
  + resource "aws_volume_attachment" "this" {
      + device_name = "/dev/sdh"
      + id          = (known after apply)
      + instance_id = (known after apply)
      + volume_id   = (known after apply)
    }

  # module.ec2.aws_instance.this[0] will be created
  + resource "aws_instance" "this" {
      + ami                                  = "ami-0c43c11b9446e99da"
      + arn                                  = (known after apply)
      + associate_public_ip_address          = true
      + availability_zone                    = "eu-west-1c"
      + cpu_core_count                       = (known after apply)
      + cpu_threads_per_core                 = (known after apply)
      + disable_api_stop                     = (known after apply)
      + disable_api_termination              = (known after apply)
      + ebs_optimized                        = (known after apply)
      + get_password_data                    = false
      + host_id                              = (known after apply)
      + host_resource_group_arn              = (known after apply)
      + iam_instance_profile                 = (known after apply)
      + id                                   = (known after apply)
      + instance_initiated_shutdown_behavior = (known after apply)
      + instance_lifecycle                   = (known after apply)
      + instance_state                       = (known after apply)
      + instance_type                        = "c5.large"
      + ipv6_address_count                   = (known after apply)
      + ipv6_addresses                       = (known after apply)
      + key_name                             = (known after apply)
      + monitoring                           = (known after apply)
      + outpost_arn                          = (known after apply)
      + password_data                        = (known after apply)
      + placement_group                      = (known after apply)
      + placement_partition_number           = (known after apply)
      + primary_network_interface_id         = (known after apply)
      + private_dns                          = (known after apply)
      + private_ip                           = (known after apply)
      + public_dns                           = (known after apply)
      + public_ip                            = (known after apply)
      + secondary_private_ips                = (known after apply)
      + security_groups                      = (known after apply)
      + source_dest_check                    = true
      + spot_instance_request_id             = (known after apply)
      + subnet_id                            = "subnet-****"
      + tags                                 = {
          + "Example"    = "ex-volume-attachment"
          + "Name"       = "ex-volume-attachment"
          + "Repository" = "https://github.com/terraform-aws-modules/terraform-aws-ec2-instance"
        }
      + tags_all                             = {
          + "Example"    = "ex-volume-attachment"
          + "Name"       = "ex-volume-attachment"
          + "Repository" = "https://github.com/terraform-aws-modules/terraform-aws-ec2-instance"
        }
      + tenancy                              = (known after apply)
      + user_data                            = (known after apply)
      + user_data_base64                     = (known after apply)
      + user_data_replace_on_change          = false
      + volume_tags                          = {
          + "Name" = "ex-volume-attachment"
        }
      + vpc_security_group_ids               = (known after apply)

      + credit_specification {}

      + enclave_options {
          + enabled = (known after apply)
        }

      + metadata_options {
          + http_endpoint               = "enabled"
          + http_put_response_hop_limit = 1
          + http_tokens                 = "optional"
          + instance_metadata_tags      = (known after apply)
        }

      + timeouts {}
    }

Plan: 3 to add, 0 to change, 0 to destroy.

Changes to Outputs:
  + ec2_arn                                = (known after apply)
  + ec2_availability_zone                  = "eu-west-1c"
  + ec2_capacity_reservation_specification = (known after apply)
  + ec2_id                                 = (known after apply)
  + ec2_instance_state                     = (known after apply)
  + ec2_primary_network_interface_id       = (known after apply)
  + ec2_private_dns                        = (known after apply)
  + ec2_public_dns                         = (known after apply)
  + ec2_public_ip                          = (known after apply)
  + ec2_tags_all                           = {
      + Example    = "ex-volume-attachment"
      + Name       = "ex-volume-attachment"
      + Repository = "https://github.com/terraform-aws-modules/terraform-aws-ec2-instance"
    }

• I have executed pre-commit run -a on my pull request

[github-actions]

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with no activity. Remove stale label or comment or this PR will be closed in 10 days

[bryantbiggs]

seems reasonable, thank you!

[antonbabenko]

This PR is included in version 5.4.0 🎉

[github-actions]

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