improving int4 asymmetric quantization accuracy (#3190)
* Fixes for asymmetric quantization
* addtional offset to further improve accuracy
* put the 0.5 into offset rather than applying it later
* update unit test for quantization
* fix format
* attempt to fix format
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Co-authored-by: Connor Holmes <connorholmes@microsoft.com>
Co-authored-by: Olatunji Ruwase <olruwase@microsoft.com>
