resource/aws_backup_selection: Automatically retry on additional IAM Role eventual consistency error (#10687)
resource/aws_backup_selection: Automatically retry on additional IAM Role eventual consistency error (#10687)

Output from acceptance testing:

```
--- PASS: TestAccAwsBackupSelection_withTags (10.70s)
--- PASS: TestAccAwsBackupSelection_basic (10.74s)
--- PASS: TestAccAwsBackupSelection_disappears (11.05s)
--- PASS: TestAccAwsBackupSelection_updateTag (16.37s)
--- PASS: TestAccAwsBackupSelection_withResources (20.65s)
```
kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,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