feat: stabilize alt_bn128 familiy of host functions

[matklad]

Feature to stabilize

This PR stabilizes three host functions: alt_bn128_g1_multiexp, alt_bn128_g1_sum, alt_bn128_pairing_check. They implement addition, scalar multiplication, and pairing check for a specific elliptic curve used in the ethereum ecosystem (eip-196).

Testing and QA

This feature underwent extensive testing:

• we had several audits
• aurora impements ethereum precompiles on top of these host functions, and those precompiles pass ethereum tests
• this PR adds a couple more tests generating using the implementation used in go-ethereum.
• we verified our costs against costs in ethereum, they are roughly comparable in terms of wall-clock time

Pre-mortem

The biggest risk I see is that we are not experts in elliptic curve crypto, so it's hard to judge if the API overall makes sense. Maybe it could be more general, maybe there are better curves, etc. However, it does fit aurora use-case and, given that the impl here is rather straightforward, even if we change something in the future, keeping the current functions won't be too onerous.

Checklist

• Link to nightly nayduck run (./scripts/nayduck.py, docs): https://nayduck.near.org/
• Update CHANGELOG.md to include this protocol feature in the Unreleased section.

[matklad]

(opened Pr from a wrong fork, re-submitted as #6824)