Add Low Precision LayerNorm

[nik-mosaic]

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[WIP] Will replace Fused LayerNorm, since Fused LayerNorm's speedup comes from running in low precision mode. Equivalent converge performance has been verified on standard NLP models (Bert, GPT).

Next commits:

• Resolve type issues
• Add test: tests/algorithms/test_low_precision_layernorm.py
• Remove FusedLayerNorm code.