Add support for import some Q&A text not need LLM to generate results

[CN-P5]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

I need to import some Q&A text，not need LLM to generate results。I add code to support uploading qa files。 Q&A text format:

Q1: 只剩一个心脏了还能活吗？
A1: 能，人本来就只有一个心脏。

Q2: 爸爸再婚，我是不是就有了个新娘？
A2: 不是的，你有了一个继母。"新娘"是指新婚的女方，而你爸爸再婚，他的新婚妻子对你来说是继母。

Q3: 樟脑丸是我吃过最难吃的硬糖有奇怪的味道怎么还有人买
A3: 樟脑丸并不是硬糖，而是一种常见的驱虫药，不能食用。虽然它的味道可能不太好，但是由于其有效的驱虫效果，所以仍然有很多人会购买。

Resolves https://github.com/langgenius/dify/issues/4664 Resolves https://github.com/langgenius/dify/issues/6904 Resolves https://github.com/langgenius/dify/issues/7735 Resolves https://github.com/langgenius/dify/issues/7430 Resolves https://github.com/langgenius/dify/issues/10873

2. Additional context or comments

No response

3. Can you help us with this feature?

• [x] I am interested in contributing to this feature.