Circom optimizations

[RogerTaule]

This PR adds a huge refactor to the stark_verifier.ejs template for both GL and BN128 circuits. Anonymous components are introduced whenever possible and many comments are added.

The following bugs are fixed in this version:

• In stark_verifier.ejs BN128, when performing the FRI evaluation if the current step is 1, s_X needs to be calculated by performing a GLMul.
• When checking the finalPol degree, we need to take into account that maxDegBits might be negative and therefore we need to force maxDegBits = 0.
• When checking merkle roots for s0, there was a typo when checking root3, which was cm2_3ns and should be cm3_2ns.

Regarding the refactor, some of the most important changes are the following:

• The FRI verification has been rewritten into a single template, which allows adds to parallelize
• _ <== has been added to be generated automatically in the template for all unused signals
• Circuits has been upgraded from 2.06 --> 2.1.0
• A small function in fft with the corresponding inverse of the roots hardcoded has been added, so that we do not have to be performing _inv operations every time.
• A lot of comments has been added to the codebase

[cla-bot[bot]]

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[cla-bot[bot]]

We require contributors @RogerTaule to read our Contributor License Agreement, please check the CLA document