Add problem statement rewriting to the rewriting pipeline

[FelixTJDietrich]

Note

This PR builds on #191, please merge afterwards
Artemis#10156 is the corresponding Artemis PR to test with

This pull request includes significant updates to the rewriting_pipeline to support multiple variants and improve functionality. The most important changes include adding a new prompt for problem statements, modifying the pipeline to handle different variants, and updating the initialization and call methods to accommodate these changes.

Support for Multiple Variants:

• app/pipeline/prompts/rewriting_prompts.py: Added a new prompt for problem statements and moved the FAQ prompt to this file.
• app/pipeline/rewriting_pipeline.py: Updated the import statements and added a variant parameter to the RewritingPipeline class. Modified the __init__ and __call__ methods to handle different prompts based on the variant. [1] [2] [3] [4] [5] [6]

Pipeline Initialization:

• app/web/routers/pipelines.py: Updated the run_rewriting_pipeline_worker and run_rewriting_pipeline functions to handle the new variant parameter, ensuring the correct pipeline variant is used. [1] [2]

Feature Descriptor Updates:

• app/web/routers/pipelines.py: Modified the get_pipeline function to return specific feature descriptors for the FAQ and problem statement variants.