Addressed review comments for issue #52 Improve description of Generative AI elements

Dear all,

please, review my changes for 
https://github.com/w3c/voiceinteraction/issues/52 Improve description of 
Generative AI elements after the review in the last session on 2024-10-23

  * section 3 Architecture
      o added a note about location of components and privacy of data
  * section 3.2 Dialog Layer
      o add a bit more about differences between traditional NLU and Gen
        AI system
  * section 3.2.5.2 LLM
      o Added characteristic of agentic applications
  * section 3.2.8.2 Dialogs
      o Spearation of usages in Traditional NLU and Generative AI systems
  * section 3.2.8.4 Intent Sets
      o Spearation of usages in Traditional NLU and Generative AI systems
  * section 3.3.1 Provider Selection Service
      o Added hint about agentic applications
  * Figure 3, figure 4
      o gray out LLM and add a justification in the text

Thank you

Dirk