[Feature] Clean up `write-kubeconfig` lock file after command finishes

[jpmcb]

What feature/behavior/change do you want?

Currently, when a kubeconfig is written using the write-kubeconfig util, the lock file is left over. Here's an example where I write a kubeconfig to my local directory tracked by git:

❯ eksctl utils write-kubeconfig --cluster beautiful-creature-1663175112 --kubeconfig ./my-kubeconfig.yaml

❯ git status

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        my-kubeconfig.yaml
        my-kubeconfig.yaml.eksctl.lock

Looking over the code, looks like this is needed so eksctl doesn't attempt multiple writes at the same time to the default kubeconfig. But it'd be great if eksctl also cleaned up this file so it's not left laying around.

Why do you want this feature?

Generally, it makes sense to me that the "behind the scenes" things are cleaned up and that the user doesn't have unexpected files from some operation.