Unable to create egress rules encompassing all ports without explicitly defining them

The `createEgressFirewallRule` API allows the creation of TCP/UDP rules involving all possible ports by simply omitting the `startport` and `endport` parameters. For instance, after the following API call:

```bash
🐞 > create egressfirewallrule networkid=bf5b51ae-c1ae-4ec5-951b-35d90d936ba2 protocol="tcp"
{
"firewallrule": {
"cidrlist": "192.168.50.0/24",
"destcidrlist": "",
"id": "fed01adb-ed94-4c60-aede-8ac53cf9aeda",
"networkid": "bf5b51ae-c1ae-4ec5-951b-35d90d936ba2",
"protocol": "tcp",
"state": "Active",
"tags": [],
"traffictype": "Egress"
}
}
```

All ports are encompassed by the egress rule:

---

However, when defining the following `cloudstack_egress_firewall` resource:

```hcl
resource "cloudstack_egress_firewall" "egress_rules" {
network_id = cloudstack_network.network.id
rule {
cidr_list = [cloudstack_network.network.cidr]
protocol = "tcp"
}
depends_on = [cloudstack_instance.vm]
}
```

The following error is returned by the provider:

```
cloudstack_egress_firewall.egress_rules: Creating...
╷
│ Error: Provider produced inconsistent result after apply
│
│ When applying changes to cloudstack_egress_firewall.egress_rules, provider "provider[\"registry.terraform.io/cloudstack/cloudstack\"]" produced an unexpected
│ new value: Root object was present, but now absent.
│
│ This is a bug in the provider, which should be reported in the provider's own issue tracker
```

A workaround is to explicitly set the `ports` argument of the `rule` block or to specify the value `all` as the protocol.

---

Thus, the user should be allowed to add a rule involving all ports by simply not specifying the `ports` argument, as it is possible via the API and UI.

If not possible to achieve so, then the `cloudstack_egress_firewall` documentation should be updated, clarifying that the `ports` argument is required for the TCP and UDP protocols.

Inizia dalla risorsa cloudstack_egress_firewall e confronta il comportamento HCL segnalato con la chiamata API createEgressFirewallRule. Verifica se è possibile supportare l’omissione delle porte per TCP o UDP; il lavoro è completato quando la risorsa accetta tale configurazione oppure la sua documentazione indica chiaramente il requisito.

Scritto dal modello di indicizzazione a partire dal testo della issue.