Add setting to enable disk buffering debug mode

[breedx-splk]

After open-telemetry/opentelemetry-java-contrib#1455 lands and is published, we will want to be able to expose this in the DiskBufferingConfiguration so that users can turn it on for troubleshooting purposes.

[Annosha]

@breedx-splk is this a beginner friendly issue? If so I'd like to work on it.

[breedx-splk]

Yes, @Annosha that is great. I'll assign to you. Thank you.