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

[russellb]

The instructlab side went in, so this can go in now once I rebase it.

[russellb]

I think I'm down to a linter fight between ruff wanting this import to move to its own first party section

+# First Party
+from instructlab.sdg import utils

but if I do that, there's another linter complaining that all of the instructlab imports aren't grouped together

[russellb]

I fixed the linter issue.