Only use persistent flags if appropriate

[twz123]

Description

These flags are used for shared functionality based on Cobra's "persistent" functions. In k0s, however, the distinction was never that clear. Persistent flags were mostly used by accident, sometimes to share flag definitions between subcommands, even if the persistent functions didn't use those flags.

Identify most (all?) of these cases and use flags instead of persistent flags. Deprecate and hide the unused persistent flags, so that they can eventually be removed.

Also remove the cwd prefixing for the restored config file in k0s restore. Relative paths are automatically resolved based on the current working directory. No need to do this manually.

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