Split `server` and `controller` tests

[lukasfrank]

Summary

This issue aims to improve the test setup of the libvirt-provider.
As the project mainly consists of two mostly independent components, the server and a controller, this parts should be individually testet.

Basic example

The server tests should include:

• Calling the machineClient to create a request
• Validate the content of the store
• Validate the existence of expected events

The controller tests should include:

• CRUD a Machine in the store
• Validate libvirt related resources eg.
  • domain xml
  • ssh into machine
  • Provide test for Exec stream with context #207
  • ...

The cloud-hypervisor-provider can be used as a reference: https://github.com/ironcore-dev/cloud-hypervisor-provider/

related issues: #380 #242 #234 #218 #217 #56