Allow deleting associated users of a user role

[rkitron]

Description

This feature adds the option delete_associated_users to user_role resource.

Motivation and Context

When SSO is enabled, and if user roles are managed by Terraform, we cannot delete a user role if users are associated with it.

How Has This Been Tested?

Checked by creating a user via Terraform, then adding a user via the console and deleting the role via Terraform.

Screenshots (if appropriate)

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist

• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes if appropriate.
• [ ] All new and existing tests passed.