Add a --kubeconfig flag in the root command

[phillebaba]

Is your feature request related to a problem? Please describe.

After working on #2497 I realized that there is no global Kubernetes configuration setting. This means that each tool is responsible for resolving the configuration file using their own hierarchy. This probably works for the most part as most tools will look for the env var $KUBECONFIG or in the path ~/.kube/config. Each individual tool seems to either define its set of possible flags but there is no guaranteed overlap. It would be a lot better to have a single place to configure Kubernetes configuration for all tools.

Describe the solution you'd like

• Given A Zarf CLI command that connects to k8s executes.
• When A --kubeconfig flag is passed in the root command.
• Then The --kubeconfig path should be used for client configuration.

Describe alternatives you've considered

The alternative would be to leave things as it is and just allow each tool to define their own hierarchy of picking up configuration.

Additional context

N/A