Validate MatMulNBits 8-bit g_idx bounds on CUDA (#31643)
This pull request improves the robustness and reliability of the CUDA
implementation for blockwise 8-bit quantized matrix multiplication in
ONNX Runtime. The main focus is on validating the group index (`g_idx`)
input to prevent out-of-bounds memory access, and on adding tests to
verify error handling for invalid group indices.
**Validation and Error Handling Improvements:**
* Added a new function `ValidateGroupIndexRangeForCuda` in
`matmul_nbits.cc` to check that all values in the `group_index` tensor
are within the valid range `[0, k_blocks)`, returning an error if any
value is out of bounds. This is called before launching the CUDA kernel.
[[1]](diffhunk://#diff-06d2e44c42a93a3c7e6b6f717115421091ee66639d0d324515042bd30d308871R37-R64)
[[2]](diffhunk://#diff-06d2e44c42a93a3c7e6b6f717115421091ee66639d0d324515042bd30d308871R634-R638)
* In the CUDA kernel `Dequantize8BitsKernelReOrder`, added an assertion
and clamping to ensure that `rid` (the group index) is within the valid
range, further protecting against invalid memory access.
**Testing Enhancements:**
* Added two new tests in `matmul_8bits_test.cc` to verify that the
operator fails as expected when `g_idx` contains out-of-range or
negative values, ensuring the new validation logic is exercised.
**Miscellaneous:**
* Included the `<vector>` header to support host-side validation logic.
These changes collectively improve the safety and reliability of
quantized matrix multiplication on CUDA by proactively catching invalid
input and providing clear error messages.
