chore: replace official Civo API client by an internal API client

[ldez]

Currently, we cannot update to the latest version of github.com/civo/civogo because it has dependencies on k8s.

• https://github.com/civo/civogo/blob/v0.2.99/go.mod -> k8s.io/client-go
• https://github.com/civo/civogo/blob/v0.3.34/go.mod -> k8s.io/api
• https://github.com/civo/civogo/blob/v0.3.38/go.mod -> k8s.io/api + k8s.io/apimachinery
• Current version -> https://github.com/civo/civogo/blob/v0.6.1/go.mod

The k8s dependencies are intricate inside the official client, I didn't find an easy forking automation to remove the dependencies.

It's useless to depend on the official client because we cannot follow it, so we will not be able to get bug fixes.

We can use a thin client based on the API documentation.

I did the migration step by step (one commit per step):

1. Create tests on the current DNSProvider by using the new mock system and using data from the API documentation to create fixture files.
2. Create a new client based on the tests created during the first step and the API documentation.
3. Replace the official client with the internal client.
4. Clean fixture files.

Each step/commit works (build and tests); there is no partial state to ensure no regression.

[dmke]

LGTM