[ET-VK] buffer implementation of rotary positional embeddings

[SS-JIA]

Stack from ghstack (oldest at bottom):

• -> [ET-VK] buffer implementation of rotary positional embeddings #15620
• [ET-VK][ez] Ensure that attn_weight buffers do not exceed GPU buffer numel limit #15651
• [ET-VK] Implementation of to_dim_order_copy #15619

Title says it all!

Differential Revision: D86340338

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15620

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❌ 2 New Failures, 1 Cancelled Job, 4 Unrelated Failures

As of commit 858e5bb with merge base d361573 ():

NEW FAILURES - The following jobs have failed:

• pull / test-multimodal-linux (gemma3-4b) / linux-job (gh)
  RuntimeError: Command docker exec -t 856c64204fe6b7f60140e3d302181a8e1f68dec8030817fd18df16b62ccd1c27 /exec failed with exit code 139
• pull / unittest-arm-backend-with-no-fvp (test_pytest_ops) / linux-job (gh)
  RuntimeError: Command docker exec -t c258eee8bd8dddd31d19ee8fa29dca4317690ead13fb7a1e31120a6b82b1953f /exec failed with exit code 1

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / test-openvino-linux / linux-job (gh)

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

• pull / unittest-editable / windows / windows-job (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following jobs failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-binary-size-linux-gcc / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / test-setup-linux-gcc / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/ops/test_conv1d.py::TestConv1d::test_qs8_conv1d_batchnorm_seq

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