Introduce out shape utils (add/stack)

[manuelcandales]

Reviewed By: georgehong

Differential Revision: D79826201

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/13199

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❌ 2 New Failures, 23 Pending, 1 Unrelated Failure

As of commit 011e298 with merge base bc5186c ():

NEW FAILURES - The following jobs have failed:

• Build documentation / build (buck2) / Build doc (gh)
  At least one of the pre-conditions you specified did not hold
• pull / test-binary-size-linux-gcc / linux-job (gh)
  /pytorch/executorch/kernels/portable/cpu/op_stack.cpp:129:26: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘ssize_t’ {aka ‘long int’} [-Werror=sign-compare]

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-static-llama-qnn-linux / linux-job (gh) (matched linux rule in flaky-rules.json)
  The process '/usr/bin/git' failed with exit code 128

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[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D79826201

[zingo]

This PR seem to have caused some build problems in the bin size tests.