add support to load kubernetes configuration for memory buffer

[DanyT]

• existing api is not changed
  • load_kube_config works as before
• extend kubeconfig_t to hold in memory buffer
• make a common flow for file/buffer code
• set fileName/buffer members accordingly
• provide new api: load_kube_config_buffer

[k8s-ci-robot]

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[ityuhui]

Thanks for your PR. I will review it.

[brendandburns]

Minor comments.

[brendandburns]

This looks good to me. Thanks for the quick turn around. I'll wait for @ityuhui to take a look though in case there are additional comments.

[ityuhui]

Thanks @brendandburns

@DanyT Can you please fix the issues reported by the code-static-check and code-sytle-check https://github.com/kubernetes-client/c/actions/runs/9781006686/job/27005098287?pr=242 in your code changes ? (Just update your code changes)

You can run the checks locally with

sh ./code-check/code-static-check.sh ./kubernetes/config/

and

find ./kubernetes/config/ -type f -regextype posix-extended -regex ".*\.(c|h)" -exec sh ./code-check/code-style-check.sh {} \;

[ityuhui]

@DanyT Could you please write an example that uses your new function so we can add it to the automated tests in case your functions are broken by future code changes. We also have memory leak testing in automated testing.

FYI https://github.com/kubernetes-client/c/blob/dc7d67098361c3579e3dd8153ccc6c4c30ddfedb/examples/Makefile#L33