SCANNPM-2 Use axios instance to re-use fetching logic

[7PH]

• Calls to fetch have been modified from

    const response = await fetch(token, {
      url: ...,
      ...getHttpAgents(proxyUrl),
    });
    // to
    const response = await fetch({
      url: ...,
    });

• An initial call to initializeAxios(properties) was added to the top of scan.ts
• Added unit tests for the init/fetch logic
• Moved http-agent.ts code to request.ts
• Used params: { .. } to pass GET params to urls

[lucas-paulger-sonarsource]

I would push to merge this first so we can address it in the respective PRs now. wdyt?

[lucas-paulger-sonarsource]

beautiful 💯