Adding unit test for sm80 prepack (#18514)
### Description
Prepacking code for block q4 x fp16 GEMM cuda kernel, for SM80 hardware
### Motivation and Context
Preparing for addition of Q4 x FP16 GEMM kernel on Nvidia Ampere GPUs.
This kernel requires sophisticated quantized weight rearrangement to
speedup loading data to tensor-core. To facilitate the addition, this
change includes the following:
1. matrix_layout.h A new layout lib that facilitate iterating matrix
elements and tiles that balance memory safety and performance.
2. prepack_sm80.h Code for rearranging quantized weight, scales and
offsets (aka. prepacking)
3. blkq4_fp16_sm80_prepack_test.cc Unit tests that explicitly test the
memory safety and correctness of the prepacking code.
Currently the prepacking code runs on CPU with single threaded code. We
run this on CPU in order to minimize GPU memory fragmentation. On the
other hand, hopefully we get around to parallelize this part of the
code. Should be straight forward with the unit tests in place.
