Reduce dependencies

[whoisjones]

• Langchain can be replaced at some point and write an own string prompt template.
• torch currently needs to be included to that tests with local models pass.
• spacy provides a convenient solution to convert spans to bio tags and back, we might want to copy and adapt our own solution.

[whoisjones]

i re-open a new issue for removing spacy at some point, torch dependency + langchain have been removed in gh-53.