Replace usage of Generators with ChatGenerators in all tutorials #356
Description
We should replace the usage of Generators with ChatGenerators in all tutorials so that users are prepared to use ChatGenerators in future and benefit from all future new features of ChatGenerators such as function calling, async, etc.
### Tasks
- [x] [27_First_RAG_Pipeline](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/27_First_RAG_Pipeline.ipynb). Code changes are drafted in [this notebook](https://colab.research.google.com/drive/1pgi2_hRe5-PPi8qsFeIaK9fKH2SZ4DAg?usp=sharing).
- [x] [28_Structured_Output_With_Loop](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/28_Structured_Output_With_Loop.ipynb)
- [x] [29_Serializing_Pipelines](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/29_Serializing_Pipelines.ipynb)
- [x] [30_File_Type_Preprocessing_Index_Pipeline](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/30_File_Type_Preprocessing_Index_Pipeline.ipynb)
- [x] [32_Classifying_Documents_and_Queries_by_Language](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/32_Classifying_Documents_and_Queries_by_Language.ipynb)
- [x] [35_Evaluating_RAG_Pipelines](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/35_Evaluating_RAG_Pipelines.ipynb)
- [x] [36_Building_Fallbacks_with_Conditional_Routing](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/36_Building_Fallbacks_with_Conditional_Routing.ipynb). Code changes are drafted in [this notebook](https://colab.research.google.com/drive/1L9BxyUmGOf4EDOSq2bkONmxRz7dKHva9?usp=sharing).
- [x] [37_Simplifying_Pipeline_Inputs_with_Multiplexer](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/37_Simplifying_Pipeline_Inputs_with_Multiplexer.ipynb). We should simply remove this tutorial because the Multiplexer component was removed in 2.4.0.
- [x] [40_Building_Chat_Application_with_Function_Calling](https://github.com/deepset-ai/haystack-tutorials/blob/main/tutorials/40_Building_Chat_Application_with_Function_Calling.ipynb)
Related issues:
- Create a version of tutorial "First QA Pipeline with RAG" using ChatGenerator #349
- Create a version of DLAI lesson "Self-Reflecting Agents with Loops" (entity extraction) using ChatGenerator haystack#8410
- Create a version of tutorial "Building Fallbacks to Websearch with Conditional Routing" using ChatGenerator #350