Invalid indexer polynomials produced when num_constraints is a power of two

[DanieleDiBenedetto]

As the title suggest, if in a circuit the number of constraints is exactly equal to a power of two, inconsistent indexer polynomials are produced. For instance:

Num constraints: 1024
a_row degree: 0
a_col degree: 1
a_val degree: 0
a_row_col degree: 1
b_row degree: 1023
b_col degree: 1
b_val degree: 1023
b_row_col degree: 1023
c_row degree: 1023
c_col degree: 1
c_val degree: 1023
c_row_col degree: 1023

This may be a porting error. Investigate and solve.

[DanieleDiBenedetto]

This issue is the same of arkworks-rs/poly-commit#40,
fixed by arkworks in arkworks-rs/poly-commit#55.
A similar fix has been commited also to our poly-commit in HorizenLabs/poly-commit@3eec3f4.
A unit test marlin side has been added too in 2589862.