Improve devx of preview scripts

[mads-hartmann]

Description

This PR is a collection of a few smaller changes that should improve the DevX of using our dev/preview scripts:

• Move the scripts around so that ./dev/preview/*.sh are all scripts that are intended to be run by the user. All other scripts are moved to util and test - this makes it easier as a developer to get an overview of what "commands" are available (we really should create a go-based CLI soon)
• Ensure all user-runnable scripts ./dev/preview/*.sh are cwd agnostic.
• Ensure the VM_NAME can be used for all user-runnable script, e.g. VM_NAME=mads-impro9290016879 ../dev/preview/ssh-vm.sh - it will still default to the VM of the branch if you don't explicitly set VM_NAME. Using this consistently means that it's easy to access a VM that's based off another branch than the one you're on (e.g. if you want to test something on the preview environment of main).
• Use VM_NAME for the kubectx name so it's possible to have multiple contexts installed in a workspace. This is useful for people (like me) who might use a single workspace to work on a lot of different branches.
• Introduces a dev/preview/list-vms.sh script so it's easier to find the names of VM for when you want to use VM_NAME. E.g. dev/preview/list-vms.sh | grep mads and then VM_NAME=xyz ../dev/preview/ssh-vm.sh

Related Issue(s)

Fixes #9713

How to test

I tested all scripts in four different ways

• with and without explicitly setting VM_NAME
  • install-k3s-kubeconfig.sh
  • ssh-vm.sh
  • port-forward-monitoring-satellite.sh
• running them from the root or from another folder (I used .werft)
  • install-k3s-kubeconfig.sh
  • ssh-vm.sh
  • port-forward-monitoring-satellite.sh

Release Notes

NONE

Documentation

N/A

[github-actions]

⚠️ Hey reviewer! BE CAREFUL ⚠️
Review the code before opening in your Gitpod. .gitpod.yml was changed and it might be harmful.

[liam-j-bennett]

🛹