java/automatic/configuration links out to pages that should be moved to docs

[zeitlinger]

https://opentelemetry.io/docs/languages/java/automatic/configuration/ links to pages in other repos, e.g. https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md#otlp-exporter-span-metric-and-log-exporters

This content should be moved to this repo.

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(Edit: @chalin)

• Move content to this repo
• Remove content from otel-java repo
• update contribution guidelines

[jaydeluca]

Referencing this comment

we'll need to make sure we add notes to the contributors guide to indicate that any new env vars / system properties need to be updated here.

could someone edit this issue's checklist and add a note to the second item to make it explicit that we need to also update the contribution guidelines?

- [ ] Remove content from otel-java repo, update contribution guidelines