feat: add support for AWS SM plaintext secrets

[jstrachan]

in addition to the key/value pair secrets

Description

currently AWS Secret Manager only supports key/value pair secrets

this PR adds the ability to define a secret as being plaintext which is common when using secrets for things like files

Motivation and Context

supports fetching plaintext secrets from AWS Secret Manager which are currently not supported

How Has This Been Tested?

I tested it against AWS Secrets Manager

Checklist

• [X] Tests
• [X] Documentation
• [X] Linting