[Duration](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/sdk-environment-variables.md#duration) input guidelines from spec and updated sdk env variables [BSP](https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/sdk-environment-variables.md#batch-span-processor). Probably we should address this after https://github.com/open-telemetry/opentelemetry-python/pull/1523 gets merged.
Duration input guidelines from spec and updated sdk env variables BSP. Probably we should address this after #1523 gets merged.