fix: fem tester update

[Krande]

• reduced integration is now considered in the fem test suite
• Code cleanup, pixi config update and minor code refactor

[github-actions]

👋 Hi there! I have checked your PR and found no issues. Thanks for your contribution!

PR Review:

I found no pr-related issues.

• ✅ PR title is ok
• ✅ Release label is ok
• ✅ SOURCE_KEY is set as a secret
• ✅ Calculated next version: "0.2.15"

Python Review:

I found no python-related issues.

Python Linting results:

• ✅ Isort
• ✅ Black
• ✅ Ruff

Python Packaging results:

• ✅ I found the CONDA_API_TOKEN secret.
• ✅ I found the PYPI_API_TOKEN secret.

Packaging Type	Package Name	Version
pyproject.toml	ada-py	0.2.14
Conda	ada-py	0.2.12
pypi	ada-py	0.2.14