When copying a kubeconfig file to your clipboard in the UI, there is no visual indication that it was successful

[markusewalker]

Setup

• Rancher version: v2.6.7-rc7
• Browser type & version: Chrome

Describe the bug

In Cluster Management, we provide the option to copy the cluster's kubeconfig to the user's clipboard. However, there is not any visual indication that once you click it, the clipboard indeed has copied the kubeconfig file. In other places of the UI, there is usually a green checkmark indicating that the clipboard has copied something.

We should do the same here so that a user will know that the clipboard has the kubeconfig currently copied into it.

To Reproduce

1. Setup Rancher and navigate to the UI in a browser.
2. In Cluster Management, click on the right ellipses and click Copy KubeConfig to Clipboard; notice that you can't tell if it is copied to the clipboard.

Result The kubeconfig file is copied to the clipboard without any visual indication.

Expected Result

There should be a green checkmark that indicates the kubeconfig has successfully been copied to the clipboard.