sycl: add CONCAT operator support

[ye-NX]

Title:
sycl: add CONCAT support for GGML_TYPE_I16 and GGML_TYPE_I32

Body:

• This PR generalizes the SYCL backend CONCAT operator to support GGML_TYPE_I16 and GGML_TYPE_I32.

• Refactors float-only kernels into templated kernels (T) for dim0/1/2 and the non-contiguous fallback.

• Replaces /4 with elem_size(dst->type) to ensure correct indexing for all types.

• Adds a type switch in ggml_sycl_op_concat to invoke concat_impl_sycl for F32, I16, and I32.

• No API changes; no behavior changes for other backends.

Testing

Built with -DGGML_SYCL=ON and verified correctness for F32, I16, I32 across dim 0/1/2/3 with both contiguous and non-contiguous inputs.

test-backend-ops passes for CONCAT.

[ye-NX]

You're right, the branch was based on an outdated master.
I’ve rebased onto upstream/master and force-pushed.

[NeoZhangJianyu]

@ye-NX
I think the PR should rebased to remove the unimpacted file, like ggufxxx.
The test-backend-op.cpp should be updated to restore the change of other legacy UT cases, except CONCAT OP.

[ye-NX]

@NeoZhangJianyu
Thank you for reviewing! I’ve addressed the feedback:
– Rebased on the latest master and removed unrelated files (gguf*, b6524/b6527).
– Restored legacy tests in tests/test-backend-ops.cpp, keeping only the CONCAT changes.

Could you please take another look?

[NeoZhangJianyu]

The test-backend-ops.cpp has many change.
It will impact other backend.

Please only add new cases, instead of changing or deleting existed cases.

Thank you!

[NeoZhangJianyu]

@ye-NX
There are 76 files to be changed. :)
Maybe you need to rebase your branch.

[max-krasnyansky]

@ye-NX There are 76 files to be changed. :) Maybe you need to rebase your branch.

Yep. Looks like ggml-opencl changes got mixed in due to incorrect/incomplete rebase.

[NeoZhangJianyu]

There are only 4 files needed.
But there are 6 empty files in this PR.
Could remove them?

[ye-NX]

@CISC , @NeoZhangJianyu
Can someone check if everything is okay now? Thanks!

[NeoZhangJianyu]

Good job!

[NeoZhangJianyu]

@ngxson
Please review again!
It's fixed for your comment.

[CISC]

@ngxson Please unblock.