feat: use generic cli args for get-kubeconfig plugin

[merll]

📝 Description

When working with different accounts from the CLI, it is useful to set one specific account on-demand using the --as-user argument. The get-kubeconfig plugin did not pass such global CLI arguments through, making it necessary having to make an extra call with set-user, and switching back after.

✔️ How to Test

There was no extra unit test written for this, as all other plugins use the same functionality.

Manual testing can be performed by adding two accounts to the Linode CLI config where each account has at least one LKE cluster.
Given that account1 has cluster1 and account2 has cluster2, making a call such as linode-cli get-kubeconfig --as-user account1 cluster1 and linode-cli get-kubeconfig --as-user account2 cluster2 will download and add two contexts to the local kubectl configuration.

Without this change, the commands return unrecognized arguments: --as-user account[1 or 2]

📷 Preview

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