Add default cluster configuration option for clean plan

[georgepstaylor]

When a cluster is imported to this module, the default configuration results in the following recurring changes to a TF Plan:

      - configuration {
          - execute_command_configuration {
              - logging    = "DEFAULT" -> null
                # (1 unchanged attribute hidden)
            }
        }

[github-actions]

TFSEC Scan Success

Show Output

```hcl

---

TFSEC will check the following folders:
.

---

Running TFSEC in .
Excluding the following checks: aws-cloudwatch-log-group-customer-key, aws-iam-no-policy-wildcards, aws-vpc-no-public-egress-sgr, aws-iam-block-kms-policy-wildcard, aws-vpc-add-description-to-security-group

======================================================
tfsec is joining the Trivy family

tfsec will continue to remain available
for the time being, although our engineering
attention will be directed at Trivy going forward.

You can read more here:
aquasecurity/tfsec#1994

timings
──────────────────────────────────────────
disk i/o 196.239µs
parsing 3.442939ms
adaptation 152.247µs
checks 15.733861ms
total 19.525286ms

counts
──────────────────────────────────────────
modules downloaded 0
modules processed 3
blocks processed 50
files read 10

results
──────────────────────────────────────────
passed 1
ignored 0
critical 0
high 0
medium 0
low 0

No problems detected!

tfsec_exitcode=0

</details> #### `Checkov Scan` Failed
<details><summary>Show Output</summary>

```hcl

*****************************

Checkov will check the following folders:
.

*****************************

Running Checkov in .
Excluding the following checks: CKV_GIT_1
terraform scan results:

Passed checks: 15, Failed checks: 1, Skipped checks: 3

Check: CKV_AWS_224: "Ensure ECS Cluster logging uses CMK"
	FAILED for resource: module.unit_test.aws_ecs_cluster.this
	File: /cluster/main.tf:1-14
	Calling File: /test/unit-test/main.tf:1-6
	Guide: https://docs.prismacloud.io/en/enterprise-edition/policy-reference/aws-policies/aws-general-policies/ensure-aws-cluster-logging-is-encrypted-using-a-customer-managed-key-cmk

		1  | resource "aws_ecs_cluster" "this" {
		2  |   name = var.name
		3  |   tags = var.tags
		4  |   setting {
		5  |     name  = "containerInsights"
		6  |     value = var.enable_container_insights
		7  |   }
		8  | 
		9  |   configuration {
		10 |     execute_command_configuration {
		11 |       logging = "DEFAULT"
		12 |     }
		13 |   }
		14 | }

github_actions scan results:

Passed checks: 208, Failed checks: 0, Skipped checks: 0


checkov_exitcode=1

CTFLint Scan Success

Show Output

*****************************

Setting default tflint config...
Running tflint --init...
Installing "terraform" plugin...
Installed "terraform" (source: github.com/terraform-linters/tflint-ruleset-terraform, version: 0.5.0)
tflint will check the following folders:
.

*****************************

Running tflint in .
tflint_exitcode=0

Trivy Scan

Show Output