Workaround k3s not loading images in agent directory when in airgapped environment

[bigtallcampbell]

This PR:

• mitigates a bug in k3s that doesn't load the images into the cluster, despite being loaded in the correct spot.
• adds functionality to automatically load the images via docker or ctr into the cluster if they are not available.
• addresses a typo in debug prestaged yamls
• updates big_red_button to remove apps that were installed
• fixes a bug where the wrong version of cfssljson was being downloaded and staged
• moves k3s-uninstall to a background thread to bypass overrides to the local environment
• doc tweaks to remove logs and tmp when doing a staging