qgemm: optimize avxvnni QGEMM inner kernel for M=1

[r-devulap]

Add specialized path for M=1 case that exploits additional available ymm registers for deeper inner kernel loop unrolling.

Performance impact (measured on 13th Gen Intel(R) Core(TM) i9-13900K):

• 30% improvement in single threaded QGEMM kernels with M = 1
• 7% reduction in average inference time on small quantized model where all kernels have M=1

|--------------------------------------------------------------------+--------+---------+----------+----------+---------+---------|
| Benchmark                                                          | Time   | CPU     | Time Old | Time New | CPU Old | CPU New |
|--------------------------------------------------------------------+--------+---------+----------+----------+---------+---------|
| QGEMM/UnsignedAPackB/M:1/N:512/K:512/Batch:1/Threads:1/real_time   | -0.275 | -0.2756 | 4330     | 3137     | 4330    | 3136    |
| QGEMM/UnsignedAPackB/M:1/N:512/K:1024/Batch:1/Threads:1/real_time  | -0.292 | -0.2927 | 9027     | 6385     | 9027    | 6385    |
| QGEMM/UnsignedAPackB/M:1/N:1024/K:1024/Batch:1/Threads:1/real_time | -0.300 | -0.3005 | 17867    | 12499    | 17866   | 12498   |
| OVERALL_GEOMEAN                                                    | -0.289 | -0.2897 |          |          |         |         |
|--------------------------------------------------------------------+--------+---------+----------+----------+---------+---------|

[r-devulap]

Posting raw qgemm benchmark numbers for clarity:

Before:

-------------------------------------------------------------------------------------------------------------
Benchmark                                                                   Time             CPU   Iterations
-------------------------------------------------------------------------------------------------------------
QGEMM/UnsignedAPackB/M:1/N:512/K:512/Batch:1/Threads:1/real_time         4330 ns         4330 ns       161969
QGEMM/UnsignedAPackB/M:1/N:512/K:1024/Batch:1/Threads:1/real_time        9027 ns         9027 ns        77210
QGEMM/UnsignedAPackB/M:1/N:1024/K:1024/Batch:1/Threads:1/real_time      17867 ns        17866 ns        39329
-------------------------------------------------------------------------------------------------------------

After:

-------------------------------------------------------------------------------------------------------------
Benchmark                                                                   Time             CPU   Iterations
-------------------------------------------------------------------------------------------------------------
QGEMM/UnsignedAPackB/M:1/N:512/K:512/Batch:1/Threads:1/real_time         3137 ns         3136 ns       221932
QGEMM/UnsignedAPackB/M:1/N:512/K:1024/Batch:1/Threads:1/real_time        6385 ns         6385 ns       109727
QGEMM/UnsignedAPackB/M:1/N:1024/K:1024/Batch:1/Threads:1/real_time      12499 ns        12498 ns        55934