Add configurable engine log level (#8067)
## Summary
- Add a top-level `log_level` config option (string, default
`"WARNING"`).
- Apply it during engine init via the already-upstream
`set_log_level_from_string` helper, so DeepSpeed logger verbosity is
config-driven instead of hard-coded.
## Test plan
- [ ] Init with `log_level="ERROR"` -> DeepSpeed logger level is ERROR.
- [ ] Omit `log_level` -> defaults to `WARNING` (no change vs. today's
effective verbosity).
Made with [Cursor](https://cursor.com)
---------
Signed-off-by: Olatunji Ruwase <tunji.ruwase@snowflake.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
