feat: optimise for pederson hash

[hellojason3]

Problem

During testing, we observed that the line let digest = self.public_input.get_hash(); consumes approximately 60GB of memory and takes around 160 seconds to run. This performance needs optimization.

Work Done

Analysis showed that most of the time is spent in the function gen_element_steps_var, which takes about 150 seconds. We optimized it by:

1.	Using global variables to replace constants, avoiding redundant calculations.
2.	Improving bitwise operation efficiency.

Result

The optimization was successful, reducing memory usage from 60GB to 3GB and execution time from 160 seconds to 27 seconds.

[hellojason3]

This is where a lot of memory and time are consumed, so I changed the way to perform bit operations.