Add SDK env variable for OTLP TLS skip verify

[pavolloffay]

What are you trying to achieve?

I would like to configure OTLP exporter in SDK with env var to skip SSL verification. The variable is not currently supported https://opentelemetry.io/docs/specs/otel/protocol/exporter/

What did you expect to see?

Additional context.

Created from open-telemetry/opentelemetry-operator#1818

[danielgblanco]

Thanks @pavolloffay , there's currently a moratorium on env vars as described in this comment

#2891 (comment)

I have added this to the Configuration SIG backlog and they will be able to pick it up as they stabilise declarative configuration.