Mistral-related models for QnA (#34045)

* mistral qna start

* mixtral qna

* oops

* qwen2 qna

* qwen2moe qna

* add missing input embed methods

* add copied to all methods, can't directly from llama due to the prefix

* make top level copied from

docs/source/en/model_doc/mistral.md

@@ -208,6 +208,11 @@ A list of official Hugging Face and community (indicated by 🌎) resources to h
 [[autodoc]] MistralForTokenClassification
     - forward
 
+## MistralForQuestionAnswering
+
+[[autodoc]] MistralForQuestionAnswering
+- forward
+
 ## FlaxMistralModel
 
 [[autodoc]] FlaxMistralModel

docs/source/en/model_doc/mixtral.md

@@ -209,3 +209,7 @@ A list of official Hugging Face and community (indicated by 🌎) resources to h
 
 [[autodoc]] MixtralForTokenClassification
     - forward
+
+## MixtralForQuestionAnswering
+[[autodoc]] MixtralForQuestionAnswering
+    - forward

docs/source/en/model_doc/qwen2.md

@@ -85,3 +85,8 @@ In the following, we demonstrate how to use `Qwen2-7B-Instruct` for the inferenc
 
 [[autodoc]] Qwen2ForTokenClassification
     - forward
+
+## Qwen2ForQuestionAnswering
+
+[[autodoc]] Qwen2ForQuestionAnswering
+    - forward

docs/source/en/model_doc/qwen2_moe.md

@@ -80,3 +80,8 @@ In the following, we demonstrate how to use `Qwen1.5-MoE-A2.7B-Chat` for the inf
 
 [[autodoc]] Qwen2MoeForTokenClassification
     - forward
+
+## Qwen2MoeForQuestionAnswering
+
+[[autodoc]] Qwen2MoeForQuestionAnswering
+    - forward