google-auth Made as optional dependency

[shivanand007]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Makes Google auth as optional dependency, gives users a option to install it separately.

Which issue(s) this PR fixes:

Fixes #2249

Special notes for your reviewer:

Does this PR introduce a user-facing change?

This change modifies the `setup.py` file to move `google-auth` to the `extras_require` section,
allowing it to be installed with `pip install kubernetes[google-auth]`.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[roycaihw]

Please add a release note with instructions of how to install google-auth going forward.

We should also make sure the tests pass. I wonder if we need to update the test pipeline to install google-auth as well.

/retest

[shivanand007]

Please add a release note with instructions of how to install google-auth going forward.

--> I have added the required release note, kindly have a review for the same.

We should also make sure the tests pass. I wonder if we need to update the test pipeline to install google-auth as well.

--> Yes, As we have Removed google-auth from requirements.txt, This must be a dependency in code which makes test cases to fail, I will check the code and see if we can make those code blocks optional as well, Additionally we have to update the test pipeline to test this use case.

/retest

[shivanand007]

@roycaihw
I have made the necessary changes in code to make google-auth as optional, Requesting to Change Test Pipeline, So That we can pass all the E2E test Cases.

[shivanand007]

/retest

[k8s-ci-robot]

@shivanand007: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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