Enable AutoRefreshKubeConfigLoader ExecPlugin support

[gregoiregermain]

Related to #317

Current behavior

The AutoRefreshKubeConfigLoader overwrites KubeConfigLoader following methods:

• _load_oid_token
• load_gcp_token

Get the expiration timestamp of the provided token and create a task than run before the token expiration.
The user authentification method with an executable:

"exec" in self._user

is not supported and the warning in the refresh_after method is not logged because the kubernetes_asyncio KubeConfigLoader._load_from_exec_plugin is not overwritten.

Desired Behavior

We should be able to get the expiration timestamp from the response of the executable and use it to make the auto refresh supporting executable plugin authentification method.

[jacobtomlinson]

Thanks for reporting this. Do you have any interest in raising a Pull Request?

[gregoiregermain]

Yes sure!

[YeppoonYIN]

Hi, any updates on the pull request? I think the default kube config generated by GKE is using exec now. This will be really helpful for new users.

[jacobtomlinson]

The classic KubeCluster was removed in #890. All users will need to migrate to the Dask Operator. Closing.