Add ability to indicate unstructured STDERR trace level

[SteveL-MSFT]

Summary of the new feature / enhancement

Currently, when a command resource is run and there is unstructured text sent to STDERR, we default to trace since we don't know if it contains sensitive information. It would be useful in the resource manifest to indicate the default trace level for unstructured STDERR content so that it can be a warn or info, for example.

Proposed technical implementation details (optional)

No response

[michaeltlombardi]

This should be incorporated into the work for adopting Open Telemetry - generating an event in the span for a resource invocation when the return data is a non-JSON string emitted to stderr.