CKV_AZURE_189 should account for empty `ip_rules`

[Matthijsy]

Describe the issue
When passing an empty ip_rules to an azurerm_key_vault this results in a Key-Vault which is not publicly available. However, CKV_AZURE_189 complains that it is publicly reachable.

Examples
This example should be approved, since it results in a non-reachable key-vault.

resource "azurerm_key_vault" "main" {
  name                          = "test"
  public_network_access_enabled = true
  purge_protection_enabled = true

  network_acls {
    bypass         =  "None"
    default_action =  "Deny"
    ip_rules = []
  }
}

Version (please complete the following information):
3.2.460