Support Python's build-in module venv for virtual environments additionally to Conda

[JohT]

🚀 Feature

• Support Python's build-in module venv for virtual environments: For those that can't use conda for example due to licensing reasons, Python's build-in venv is now supported additionally. The advantage of it is that you don't need to install any additional tools.

⚙️ Optimization

• Move environment.yml into the root directory
• Rename environment.yml to conda-environment.yml
• Cache Python pip packages when venv is used
• Skip anomaly detection for less than 15 nodes.
• Tweak optimization trials and summary logs for anomaly detection.