[PERFORMANCE] Optimize some additional small convolution paths

[sdatkinson]

Summary

Adds specialized fast paths for other small convolution shapes:

• Adds unrolled Conv1D paths for 8x4 and 1x4 channel layouts.
• Expands Conv1x1 optimized paths for 4x4 with fused bias, 4x6, and 8x6.
• Enables NAM_USE_INLINE_GEMM for tool/test targets that exercise these paths.
• Adds reference-comparison tests for the new optimized convolution cases.

Testing

• Added coverage in tools/test/test_conv1d.cpp for:
  • 8x4, kernel size 6, dilation 3
  • 1x4, kernel size 16
• Added coverage in tools/test/test_conv_1x1.cpp for:
  • 4x6
  • 8x6
  • 4x4 with bias