fix: Remove any secretsmanager:* permissions if no secret ARNs are provided to IRSA external-secrets permissions

[ohookins]

Description

Applies the same dynamic trick to the secretsmanager part of the external secrets role policy, so that if we don't grant access to any secrets we don't end up with an apply error.

Motivation and Context

Without supplying any values for var.external_secrets_secrets_manager_arns we end up with a policy statement like this:

                  + {
                      + Action = [
                          + "secretsmanager:ListSecretVersionIds",
                          + "secretsmanager:GetSecretValue",
                          + "secretsmanager:GetResourcePolicy",
                          + "secretsmanager:DescribeSecret",
                        ]
                      + Effect = "Allow"
                    },

This is invalid since it lacks resources and cannot be applied.

Breaking Changes

No breaking change.

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

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

It's such a trivial change I don't believe these are necessary but can circle back to these if you like.

[antonbabenko]

This PR is included in version 6.1.1 🎉