CUDA kernel sync fixes, test_layer enhancement

[Cydral]

Summary

This PR addresses critical CUDA synchronization issues and enhances the test_layer utility function.

CUDA Kernel Fixes

Several CUDA kernels were using __syncthreads() for cross-block synchronization, which is incorrect since __syncthreads() only synchronizes threads within the same block, not across different blocks. When grid_stride_range_y distributes work across multiple blocks, these synchronization barriers fail silently.

Affected functions decomposed into separate kernels:

• inverse_norms()
• dot_prods()
• multiply_conv()
• layer_normalize()
• rms_normalize()
• compute_act_halt_probabilities()

The fix replaces intra-kernel __syncthreads() with sequential launch_kernel() calls, which provide implicit synchronization between kernel executions.

test_layer Enhancement

Modified test_layer to accept optional parameters for testing layers with specific tensor input constraints, enabling proper gradient verification for layers that require particular input dimensions.

Related Discussion

Follow-up to #3128

[Cydral]

@davisking, Hi Davis, once PR #3132 is resolved, I will be able to share a full update for the ACT processing layer.