feat: actionable error on non-ARN policy

[hoffa]

Issue #, if available

Description of changes

Value is passed to ManagedPolicyArns which must be ARNs:

serverless-application-model/samtranslator/model/role_utils/role_constructor.py

Lines 153 to 154 in b154e38

	if policy_arn not in managed_policy_arns:
	managed_policy_arns.append(policy_arn)

serverless-application-model/samtranslator/model/role_utils/role_constructor.py

Line 164 in b154e38

execution_role.ManagedPolicyArns = list(managed_policy_arns)

If it's a string but not an ARN, the deployment will fail either way, so it's backward compatible for us to fail instead with a more helpful error.

Description of how you validated changes

Checklist

• Adheres to the development guidelines
• Add/update transform tests
  • Using correct values
  • Using wrong values
• Add/update integration tests

Examples?

Please reach out in the comments if you want to add an example. Examples will be
added to sam init through aws/aws-sam-cli-app-templates.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.