sha2 air formulas optimizations

[Okm165]

Summary

This PR introduces an optimization for the SHA-2 precompile AIR constraints, reducing the size of the SHA-2 columns by 22.

Core Idea

The optimization is based on leveraging equivalent expressions for the SHA-2 ch and maj functions to simplify the constraints:

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• ch optimization:

  ch := (e AND f) XOR (NOT e AND g)  
     = g XOR (e AND (f XOR g))
  

Eliminates single NOT operation.

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• maj optimization:

  maj := (a AND b) XOR (a AND c) XOR (b AND c)  
      = (a AND (b XOR c)) XOR (b AND c)
  

Eliminates single AND operation.