Load environment variables from SecretsManager

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**Tell us about your request**
I would love if Lambda support loading values for environment variables from SecrtesManager like ECS does. This would prevent varaibles to be visible in the Lambda console but still make them easily usable inside my function code.

**Which service(s) is this request for?**
AWS Lambda, Secretsmanager

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
see above

**Are you currently working around this issue?**
Currently, I can use environment encryption to partly solve that.

**Additional context**
N/A

**Attachments**
N/A