A `transform` pass to lower `BF16` type `vector.contract` to
`vector.fma` using `AVX2` BF16 packed operations:
- `vbcstnebf162ps` - Broadcasts BF16 into packed F32.
- `vcvtneebf162ps` - Convert packed BF16 even-indexed elements into
packed F32.
- `vcvtneobf162ps` - Convert packed BF16 odd-indexed elements into
packed F32 Data.
