refactor: refactor processors folder structure

[Henrrypg]

This pull request reorganizes the processor modules in the openedx_ai_extensions package to improve code structure and maintainability. The main changes involve moving LLM-related processor files into a dedicated llm subpackage, updating imports throughout the codebase, and adjusting test mocks accordingly.

New proposed structure:

📦processors
┣ 📂llm
┃ ┣ 📂providers
┃ ┃ ┗ 📜__init__.py
┃ ┣ 📜__init__.py
┃ ┣ 📜educator_assistant_processor.py
┃ ┣ 📜litellm_base_processor.py
┃ ┗ 📜llm_processor.py
┣ 📂openedx
┃ ┣ 📂utils
┃ ┃ ┣ 📜__init__.py
┃ ┃ ┗ 📜component_extractors.py
┃ ┣ 📜__init__.py
┃ ┣ 📜content_libraries_processor.py
┃ ┣ 📜openedx_processor.py
┃ ┗ 📜submission_processor.py
┗ 📜__init__.py

This solves #88

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.58%. Comparing base (5e02075) to head (dad77a8).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #100   +/-   ##
=======================================
  Coverage   90.58%   90.58%           
=======================================
  Files          47       47           
  Lines        4310     4310           
  Branches      271      271           
=======================================
  Hits         3904     3904           
  Misses        317      317           
  Partials       89       89           

Flag	Coverage Δ
unittests	90.58% <ø> (ø)

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