[openapi] refactor render related openapi [3/N]

[andyxning]

Purpose

This is the third pr for #31164.

1. refactor render related openapi to raise exception directly.
2. refactor OpenAIServingRender's create_error_response to the one in vllm.entrypoint.utils.

Test Plan

Test Result

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
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