[Feature]: add support for `OTEL_PROPAGATORS` environment variable

[jan-xyz]

Related Problems?

We use this environment var via a provided configmap from the platform to have a consistent propagator in our Kubernetes cluster. I would be nice to also have the support for it in the rust ecosystem.

Describe the solution you'd like:

Automatically configuring the Propagator based on the OTEL_PROPAGATORS environment variable instead of a noop propagator.

Considered Alternatives

No response

Additional Context

No response

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[scottgerring]

Hey @jan-xyz thanks for the report!

Here's a link to the relevant bit of the spec.