Seperating pyproject.toml dependencies

[rdziewietin]

Primarily, this pull request:

• Moves some functions that do not relate to DocTR out of doctr.ocr_functions and moves them to data.post_processing
• Separates the DocTR and LLM dependencies into app-doctr and app in the pyproject.toml
• Moves evaluate_cells into post-processing and adds a test

I tested it locally and with Docker. Both of them work and Docker building is significantly faster. Let me know if it works for y'all.

[ginic]

Thanks, @rdziewietin ! This is a really helpful way to reorganize the code and more unit tests are chef's kiss!

I just have one minor suggestion about removing an unused function.

[ginic]

Looks great! Thank you!