Rename package to `instructlab.sdg` from `instructlab_sdg`

[russellb]

Part of issue #2

This changes to use Python namespace packages where instructlab is the namespace used for our libraries.

Signed-off-by: Russell Bryant rbryant@redhat.com

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• [ ] Depends on https://github.com/instructlab/instructlab/pull/1263

[russellb]

this branch shouldn't have been pushed to this repo, sorry