tests/resource/aws_ecr_repository: Implement sweeper (#12834)
tests/resource/aws_ecr_repository: Implement sweeper (#12834)

Output from sweeper in AWS Commercial:

```
2020/05/11 19:35:10 [DEBUG] Running Sweepers for region (us-west-2):
2020/05/11 19:35:10 [DEBUG] Running Sweeper (aws_ecr_repository) in region (us-west-2)
...
2020/05/11 19:35:12 [INFO] Deleting ECR repository: tf-acc-test-ecr-jynnb8fr46
2020/05/11 19:35:13 [INFO] Deleting ECR repository: tf-acc-test-lifecycle-eynj6yvxr7
2020/05/11 19:35:13 [INFO] Deleting ECR repository: tf-acc-test-lifecycle-8c7g6nd8fe
2020/05/11 19:35:13 [INFO] Deleting ECR repository: tf-acc-test-ecr-xkk8bx2mxz
2020/05/11 19:35:14 [INFO] Deleting ECR repository: tf-acc-test-lifecycle-fmlgi1nwzb
2020/05/11 19:35:14 [INFO] Deleting ECR repository: tf-acc-test-lifecycle-vm96ysp8bc
2020/05/11 19:35:15 [INFO] Deleting ECR repository: tf-acc-test-ecr-ba2v8fhova
2020/05/11 19:35:15 [INFO] Deleting ECR repository: tf-acc-test-6050143170194165363
2020/05/11 19:35:16 [INFO] Deleting ECR repository: tf-acc-test-ecr-ff08cszgny
2020/05/11 19:35:16 [INFO] Deleting ECR repository: tf-acc-test-ecr-se3ehbyrhb
2020/05/11 19:35:16 [INFO] Deleting ECR repository: tf-acc-test-6889266986464638074
2020/05/11 19:35:17 [INFO] Deleting ECR repository: tf-acc-test-ecr-o2t30n9cnx
2020/05/11 19:35:17 [INFO] Deleting ECR repository: bar
2020/05/11 19:35:18 [INFO] Deleting ECR repository: tf-acc-test-ecr-04h02y7eg3
2020/05/11 19:35:18 [INFO] Deleting ECR repository: tf-acc-test-4382088656668134051
2020/05/11 19:35:19 [INFO] Deleting ECR repository: tf-acc-test-lifecycle-i7l3dvpph9
2020/05/11 19:35:19 [INFO] Deleting ECR repository: tf-acc-test-1524363012416375905
2020/05/11 19:35:19 Sweeper Tests ran successfully:
	- aws_ecr_repository
2020/05/11 19:35:19 [DEBUG] Running Sweepers for region (us-east-1):
2020/05/11 19:35:19 [DEBUG] Running Sweeper (aws_ecr_repository) in region (us-east-1)
...
2020/05/11 19:35:21 [INFO] Deleting ECR repository: tf-acc-test-ecr-1lkbnobdkl
2020/05/11 19:35:21 [INFO] Deleting ECR repository: tf-acc-test-ecr-q3ungwfsrb
2020/05/11 19:35:21 Sweeper Tests ran successfully:
	- aws_ecr_repository
ok  	github.com/terraform-providers/terraform-provider-aws/aws	14.934s
```

Output from sweeper in AWS GovCloud (US):

```
2020/05/11 19:35:32 [DEBUG] Running Sweepers for region (us-gov-west-1):
2020/05/11 19:35:32 [DEBUG] Running Sweeper (aws_ecr_repository) in region (us-gov-west-1)
...
2020/05/11 19:35:35 Sweeper Tests ran successfully:
	- aws_ecr_repository
ok  	github.com/terraform-providers/terraform-provider-aws/aws	4.519s
```
terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws