Tests with AzureCredentialsFact are skipped on Windows

[gregkalapos]

Follow up from https://github.com/elastic/apm-agent-dotnet/pull/1702#pullrequestreview-976588383.

Current situation:

• Tests with AzureCredentialsFact run on Linux
• Those don't run on Windows
• The skip reason on Windows is: Azure credentials not available. If running locally, run 'az login' to login
• AzureCredentials.cs does the parsing of the credentials which seem to end up with Unauthenticated
• AzureCredentials.cs uses console log and the logging is limited

TODO:

• Ultimately run tests with AzureCredentialsFact on Windows as well
• And in order to diagnose:
  • Use XUnit logger to better log collection in CI instead of console logs
  • Extend logging in AzureCredentials.cs