env var to set loglevel for python logging

Is there a way to set the `loglevel` through an env var?
This would be especially useful for lambda-docker.
We would like to be able to filter out a lot of noise and only see our app logs, at least during development.

該 issue 沒有指出檔案、測試或進入點。先找出 emulator 的記錄設定與環境變數處理邏輯，然後確認所要求的變數會變更記錄層級並篩選開發環境輸出，同時不會抑制應用程式記錄。

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