[websocket]: Fix asprintf return value handling in websocket client (IDFGH-16571)

[gabsuren]

Description

The websocket client code was calling asprintf() functions without checking their return values, which triggered -Werror=unused-result compiler warnings. The asprintf() function returns -1 on memory allocation failure, but the original code ignored this return value, potentially leading to potential crashes or undefined behavior

Testing

esp-protocols CI pipeline execution

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Checklist

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• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

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