Add swap_size to instance_spec config

[yec-akamai]

📝 Description

swap_size was a missing attributes. Adding it to the linode_instance_spec and allow user to specify it when creating a Linode.

✔️ How to Test

make TEST_ARGS="-v instance_booted" test

Manual Test:

1. In a sandbox environment, i.e. dx-devenv, run the following playbook:

    - name: Create a booted Linode instance
      linode.cloud.instance:
        label: ansible-test-instance
        region: us-ord
        type: g6-standard-1
        image: linode/ubuntu22.04
        root_pass: Fn$$oobar123
        private_ip: true
        booted: true
        swap_size: 512
        state: present

2. Observe that the linode instance is created successfully. (swap_size won't be returned in the response though.)

[zliang-akamai]

I am surprised we didn't have this, lol

[zliang-akamai]

LGTM!

[ykim-akamai]

LGTM, nice work