Selective dequantization (#5375)
This PR adds a new functionality for the dequantizer function, called
`selective_dequantize`, which enables partially dequantizing a
3-dimensional matrix in case we don't need to dequantize all the data
from lower bit (like fp8/fp6) to bf16.
I also added a unit test to check its functionality.
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Co-authored-by: Reza Yazdani <reza.yazdani@snowflake.com>
Co-authored-by: Logan Adams <114770087+loadams@users.noreply.github.com>
