Prevent leaking global flags from dependencies

[twz123]

Description

It may happen that dependencies used by k0s will add their own global flags, which then end up in k0s's flags. Add a unit test that verifies that no unwanted flags are leaking. Move the workarounds for hiding unavoidable flags into the appropriate places. The kubectl code wasn't responsible for those, but the k0s cloud provider code was.

See also:

• Bump Kubernetes to v1.27 #2879
• Externalize k0s cloud provider #2906

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual test
• Auto test added

Checklist:

• My code follows the style guidelines of this project
• My commit messages are signed-off
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings