Update VM/Containers exercise for WS25/26

[MakisH]

Description

Updates the exercise for Virtual Machines and Containers for this year.

Main changes:

• Switches to Alpine as the default recommendation, mainly to save bandwidth during the exercise (closes Change VM distribution to something more lightweight like Alpine Linux #201). Ubuntu Server remains offered as an alternative.
• Adds details for Apple Silicon and details on the compatibility versions between Vagrant and VirtualBox.
• Adds details for installing Alpine and running neofetch in it. Since at the moment only fastfetch is available, both are mentioned.
• Makes preparatory steps more prominent, moves important notes earlier.

Checklist

• I made sure that the markdown files are formatted properly.
• I made sure that all hyperlinks are working.