Fix aws CLI auto-completions, use smaller kubectl package

[Nuru]

what

• Fix aws auto-completion
• Only install latest kubectl

why

• The aws CLI is provided in 2 versions, v1 and v2, and which version is in use is managed by update-alternatives. However, each version of the CLI has a corresponding version of the aws_completer utility to perform auto-completion, but until now, Geodesic always used the v1 completer (a python script), even with the v2 CLI. This mostly worked, but it is not supported or correct.
• Previously, we installed the kubectl package from packages.cloud.google.com, which is over 200 MB because it installs multiple versions of kubectl. We now install only the latest kubectl package from the Cloud Posse package repo, which is under 50 MB, to save space. Cloud Posse publishes packages for each minor version of kubectl (e.g. kubectl-1.29) so you can install the latest version compatible with your cluster if you do not want the current latest version.

references

This was brought to our attention by aws/aws-cli#8547 since upgrading to Python 3.12 in Geodesic v2.9.0.