Fix: GLV exponentiation in GT with large exponents

[ThomasPiellard]

Description

• ExpGLV on 𝔽_{q}* /(𝔽_{q}*)ʳ uses max(len(s1), len(s2)) in the main loop (as in G1 and G2)
• mulWindowed failed for negative exponents ( [-s]G returned [s]G), the PR also fixes this.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How has this been tested?

• Added a test that was previously failing with a big exponent for ExpGLV
• Added a test to check the property [-s]G=-[s]G

Checklist:

• I have performed a self-review of my code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[github-actions]

Summary

✅ Passed: 5883
❌ Failed: 0
🚧 Skipped: 5

🚧 Skipped

• TestReference (github.com/consensys/gnark-crypto/ecc/bn254/fr/sis)
• TestLimbDecomposition (github.com/consensys/gnark-crypto/ecc/bn254/fr/sis)
• TestAppend (github.com/consensys/gnark-crypto/ecc/bn254/fr/tensor-commitment)
• TestAppendSis (github.com/consensys/gnark-crypto/ecc/bn254/fr/tensor-commitment)
• TestCommitmentSis (github.com/consensys/gnark-crypto/ecc/bn254/fr/tensor-commitment)

[github-actions]

Summary

✅ Passed: 5883
❌ Failed: 0
🚧 Skipped: 5

🚧 Skipped

• TestReference (github.com/consensys/gnark-crypto/ecc/bn254/fr/sis)
• TestLimbDecomposition (github.com/consensys/gnark-crypto/ecc/bn254/fr/sis)
• TestAppend (github.com/consensys/gnark-crypto/ecc/bn254/fr/tensor-commitment)
• TestAppendSis (github.com/consensys/gnark-crypto/ecc/bn254/fr/tensor-commitment)
• TestCommitmentSis (github.com/consensys/gnark-crypto/ecc/bn254/fr/tensor-commitment)

[yelhousni]

All looks good 👍
The last two commits just fix few typos and some cosmetics:

• merges the new (exp, expGLV) with the old (exp, expGLV and CyclotomicExp) test;
• uses genA variable to switch GenE12() for GenE24() or GenE6() when needed;
• uses {{ toUpper .Name}} for curves' names instead of BN254 in the new test;
• manually apply the fix (and test) to BLS24-* and BW6-* as the towers are not auto-generated there.

[gbotrel]

@yelhousni @ThomasPiellard this snippet is weird? didn't review this PR but to me this code is useless.
What does this code do; assign a *big.Int, overwrites it with an object from a pool, and Neg(s) into e, the object of the pool before discarding it.