[test] Allow to use different linode uri

[Michkov]

• Get linode token and url from linode secret under kube-system
• Count number of nodes using chainsaw function
• Allow to define KUBECONFIG file in Makefile

General:

• Have you removed all sensitive information, including but not limited to access keys and passwords?
• Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

Pull Request Guidelines:

1. Does your submission pass tests?
2. Have you added tests?
3. Are you addressing a single feature in this PR?
4. Are your commits atomic, addressing one change per commit?
5. Are you following the conventions of the language?
6. Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. Have you explained your rationale for why this feature is needed?
8. Have you linked your PR to an open issue

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.11%. Comparing base (e1b061c) to head (b61d821).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #371   +/-   ##
=======================================
  Coverage   73.11%   73.11%           
=======================================
  Files          23       23           
  Lines        2648     2648           
=======================================
  Hits         1936     1936           
  Misses        585      585           
  Partials      127      127           

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[Michkov]

replaced by #372