[ET-VK][11/n] copy_channel_offsets node

[yipjustin]

Stack from ghstack (oldest at bottom):

• #3388
• -> #3351

1. Add a node copy_channel_offsets specifically for copying along the channel dimension, it needs extra attention at the boundaries due to channel packing. 1.1. copy_channel_offsets will be useful for aten.cat and aten.split.
2. Create etvk.* operators to facilitate testing. Add test case for both copy_offset and copy_channel_offset.

Differential Revision: D56554426

[pytorch-bot[bot]]

:link: Helpful Links

:test_tube: See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/3351

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As of commit 7a25897934934c44a37cd31744c002bbf51ba641 with merge base e5471a5a7ade0f09b383e9ef1403cff73a0ccd1f (): :green_heart: Looks good so far! There are no failures yet. :green_heart:

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This pull request was exported from Phabricator. Differential Revision: D56554426

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This pull request was exported from Phabricator. Differential Revision: D56554426

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This pull request was exported from Phabricator. Differential Revision: D56554426

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This pull request was exported from Phabricator. Differential Revision: D56554426

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This pull request was exported from Phabricator. Differential Revision: D56554426

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This pull request was exported from Phabricator. Differential Revision: D56554426

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This pull request has been merged in pytorch/executorch@ae250c03a9f744db2fa20009426fc3659b59815f.