[Bugfix]: make most of test_openai_schema.py pass

This change makes most of the parameterized tests in `pytest
tests/entrypoints/openai/test_openai_schema.py` pass. We handle user input
errors, enrich HTTP error messages with more information, and update the error
response definitions for several API endpoints.

The remaining tests that fail are `POST /tokenize` and maybe `POST
/v1/chat/completions`.

FIX #17037
FIX #17038

Signed-off-by: David Xia <[email protected]>

Author: davidxia