fix: bound vector store file polling (#3401)

Fixes #3097

## Summary
- add an optional `max_wait_seconds` bound to
`vector_stores.files.poll()`
- thread the same bound through sync/async `create_and_poll()` and
`upload_and_poll()`
- raise `TimeoutError` instead of waiting forever when a vector store
file stays `in_progress`

## Why
`upload_and_poll()` currently waits until the vector store file reaches
a terminal state. If the backend leaves the vector store file in
`in_progress` indefinitely, the helper never returns and the caller has
no SDK-level escape hatch. The new argument keeps the default behavior
unchanged, while letting callers opt into a bounded wait.

## Validation
- `PYTHONPATH=src python -m pytest
tests/api_resources/vector_stores/test_files.py::TestFiles::test_poll_timeout
tests/api_resources/vector_stores/test_files.py::TestAsyncFiles::test_poll_timeout
-q`
- `PYTHONPATH=src python -m pytest
tests/api_resources/vector_stores/test_files.py::test_create_and_poll_method_in_sync
tests/api_resources/vector_stores/test_files.py::test_upload_and_poll_method_in_sync
-q`
- `PYTHONPATH=src python -m ruff check
src/openai/resources/vector_stores/files.py
tests/api_resources/vector_stores/test_files.py`
- `python -m compileall -q src/openai/resources/vector_stores/files.py
tests/api_resources/vector_stores/test_files.py`
- `git diff --check`

- [x] I understand that this repository is auto-generated and my pull
request may not be merged

Co-authored-by: Marcus Wood <marcuswood@openai.com>