[Feature]: append firewall rule on firewall

Nobody has claimed this yet.

### Description

Running example playbook will result in firewall rule1 to dissapear from the firewall and rule2 to be the only one enforced.
I'm looking for a way to not be required to repeat the entire existing firewall config

### New/Affected Components

linode.cloud.firewall

### Example Ansible Config

```
- name: test linode firewall
gather_facts: false
hosts: localhost
tasks:
- name: Create a Linode Firewall1
linode.cloud.firewall:
label: "test_linode"
rules:
inbound:
- label: "test1"
addresses:
ipv4:
- "1.1.1.1/32"
description: "test1"
ports: 1
protocol: TCP
action: ACCEPT
outbound_policy: ACCEPT
inbound_policy: ACCEPT
state: present
- name: Create a Linode Firewall2
linode.cloud.firewall:
label: "test_linode"
rules:
inbound:
- label: "test2"
addresses:
ipv4:
- "2.2.2.2/32"
description: "test2"
ports: 2
protocol: TCP
action: ACCEPT
state: present
```

Start with the supplied Ansible playbook and the linode.cloud.firewall component, reproducing the two tasks against the same firewall label. Trace how the second task handles the existing inbound rules and determine the expected append behavior. Done means the second task preserves rule1 while enforcing rule2, without requiring the full existing configuration to be repeated.

Written by the indexing model from the issue text.