TPT-3319: Add support for Apply Linode Firewalls

[jcallahan-akamai]

📝 Description

This adds support for the POST /linode/instances/:id/firewalls/apply endpoint.

https://techdocs.akamai.com/linode-api/reference/post-apply-firewalls

✔️ How to Test

Code example:

    client = LinodeClient(os.getenv("LINODE_TOKEN"))

    # linode_id = YOUR LINODE ID

    linode = Instance(client, linode_id)
    linode.apply_firewalls() # Returns True if successful 

Integration test:

make TEST_CASE=test_linode_apply_firewall testint

Unit tests:

make testunit

[lgarber-akamai]

Tests are passing on my end, nice work!

[jriddle-linode]

LGTM working locally!

[ykim-akamai]

LGTM, just pushed a commit to fix test image due to debain10 image being deprecated.