hashicorp/packer-plugin-azure

AI Summary: Implement a new configuration option (`build_key_vault_secret_delete`) for the Packer Azure plugin to allow deleting secrets from Azure Key Vault after use. This addresses the issue of accumulating secret versions and exceeding Key Vault backup limits. The implementation should safely delete the secret only when the `build_key_vault_name` is provided and the new option is set to `true`.