[RELAND] [CUDA graphs] Make CUDAGeneratorImpl capturable (ci-all edition)

[mcarilli]

Resubmission of #47989 with attempted fix for the unexpected context creation that caused revert (#47989 (comment)).

Submitting from a ci-all branch because the failing test isn't public.

Diffs relative to master should be the same as #47989 's approved diffs, aside from the fix itself a5c80f6.

[dr-ci]

💊 CI failures summary and remediations

As of commit 28d5a21 (more details on the Dr. CI page):

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✅ None of the CI failures appear to be your fault 💚

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• 2/2 broken upstream at merge base b2ec21a from Dec 01 until Dec 02 (32 commits; 27905df - 022c929)

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🚧 2 fixed upstream failures:

These were probably caused by upstream breakages that were already fixed.

Please rebase on the viable/strict branch (expand for instructions)

Since your merge base is older than viable/strict, run these commands:

git fetch https://github.com/pytorch/pytorch viable/strict
git rebase FETCH_HEAD

Check out the recency history of this "viable master" tracking branch.

• pytorch_linux_xenial_cuda10_2_cudnn7_py3_slow_test from Dec 01 until Dec 02 (35 commits; 27905df - bdb68d9)
  • 🔁 rerun
• pytorch_paralleltbb_linux_xenial_py3_6_gcc5_4_test from Dec 01 until Dec 02 (32 commits; 27905df - 022c929)
  • 🔁 rerun

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This comment has been revised 4 times.

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@ngimel has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

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@ngimel merged this pull request in 31808dc.