fix use TM_LOG_LEVEL environment variable first

[zhyncs]

Motivation

use TM_LOG_LEVEL environment variable first

When I want to print the Turbomind's debug log, I set TM_DEBUG_LEVEL=DEBUG and TM_LOG_LEVEL=DEBUG. It doesn't work and I find that I must use the --log-level DEBUG command line argument. It's very unintuitive.

Modification

Set log level for Turbomind only when environment variable TM_LOG_LEVEL has not been set. After this modification, when environment variable TM_LOG_LEVEL has been set, use it first rather than the command line config or the default config.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[zhyncs]

Hi @lzhangzz @AllentDan @lvhan028 May you help review this pr? Thanks.

[zhyncs]

ping @lvhan028

[lvhan028]

busy with v0.2.2 release now, no rush

[lvhan028]

May do the same change in api.py

[zhyncs]

May do the same change in api.py

ok

[zhyncs]

May do the same change in api.py

done