Add support for custom extraArgs to kine process

[mback2k]

Description

Enables configuration of datastore-max-open-connections and other datastore specific options which could be essential.

I am currently having huge issues with my k0s due to kine exhausting the max connections on my MySQL backend server. I am constantly receiving errors like Error 1203 (42000): User kine already has more than 'max_user_connections' active connections which is 50.

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

[twz123]

Thank you! There's currently another PR in review for this: #5871

[mback2k]

Closing in favor of #5871. Thanks for the hint.