normalize json before deduplicating in `ToolEngine.tool_response_to_str`

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### Dify version

1.17.1

### Cloud or Self Hosted

Self Hosted (Docker)

### Steps to reproduce

1. connect to a swagger mcp that returns compact json object
2. let agent to call that tool
3. check tool call history, finding two duplicated objects, a compact one and another formatted one

### ✔️ Expected Behavior

It should be deduplicated as documented in the function.

### ❌ Actual Behavior

Objects are duplicated.