[NJT] Allow construction of NJT within graph using offsets from inputs

[soulitzer]

Stack from ghstack (oldest at bottom):

• -> [NJT] Allow construction of NJT within graph using offsets from inputs #124624
• Do not import transformers when import torch._dynamo #124634
• [NJT] Inline through torch.nested.nested_tensor_from_jagged instead of graph break #124343

Creating symbolic nested ints within the graph is difficult. Using unbacked symints should solve the most important(?) cases in the mean time.

See #118446

Known gaps:

• creating NJT from intermediate offsets (offsets created within the graph, as opposed to being offsets passed in as inputs)
• when the same offsets is also passed in as a input to the graph. We are not smart enough to realize that the offsets from that input is the same and therefore would fail when the sizes are compare ("s0 cannot be compared with u0")

cc @voznesenskym @penguinwu @EikanWang @jgong5 @Guobing-Chen @XiaobingSuper @zhuhaozhe @blzheng @wenzhe-nrv @jiayisunx @chenyang78 @kadeng @chauhang

[pytorch-bot]

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❌ 1 New Failure

As of commit 044eaaf with merge base bad8d25 ():

NEW FAILURE - The following job has failed:

• Lint / lintrunner-noclang / linux-job (gh)
  >>> Lint for torch/nested/_internal/nested_tensor.py:

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[jbschlosser]

why would this path ever be hit if we manually update the registry for fake tensors during tensor_unflatten?

[davidberard98]

@pytorchbot rebase

[pytorchmergebot]

@pytorchbot started a rebase job onto refs/remotes/origin/viable/strict. Check the current status here

[pytorchmergebot]

Rebase failed due to Command git -C /home/runner/work/pytorch/pytorch rebase refs/remotes/origin/viable/strict gh/soulitzer/296/orig returned non-zero exit code 1

warning: skipped previously applied commit 20048a0e48c
warning: skipped previously applied commit b5400b8fd89
hint: use --reapply-cherry-picks to include skipped commits
hint: Disable this message with "git config advice.skippedCherryPicks false"
Rebasing (1/1)
Auto-merging test/dynamo/test_subclasses.py
Auto-merging test/test_fake_tensor.py
CONFLICT (content): Merge conflict in test/test_fake_tensor.py
Auto-merging test/test_nestedtensor.py
Auto-merging torch/nested/_internal/nested_tensor.py
error: could not apply 0ac80a38671... [NJT] Allow construction of NJT within graph using offsets from inputs
hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
hint: You can instead skip this commit: run "git rebase --skip".
hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Could not apply 0ac80a38671... [NJT] Allow construction of NJT within graph using offsets from inputs

Raised by https://github.com/pytorch/pytorch/actions/runs/9274613146