Big optmizations to ecAdd, ecMul and ecPairing and small refactor

[hecmas]

This PR contains the following significative optimizations:

• ecMul.zkasm calls to ecAdd.zkasm now to avoid unnecessary checks.
• Added a new file doublePointBN254.zkasm to perform doublings.
• ecMul.zkasm now does not use any binary to perform the scalar k reconstruction.
• A new file bitwiseReconstruction.zkasm has been added to allow "fill in" the missing bits of a particular $256$-bit number.
• Some files renaming, to be more consistent with the theory; e.g., instead of scalarMulBN254, we now use scalarMulFP2BN254 to put emphasy on the underlying finite field.
• All scalar reconstructions have been optimized with the slogan: "focus on verifying, not computing".
• Minor optimizations and reorganizations of the code.
• A new function has been added to perform point scalar multiplication by $6 x^2$ directly, where $x$ is the BN254 generator parameter.
• Added explicit counters for ecAdd, ecMul and ecPairing.

[sonarcloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud