perf(ecmul): use GLV with safe handling of edge cases in EVM ecmul

[yelhousni]

Description

Another tiny PR to use GLV with safe handling of edge cases in EVM ecmul precompile.

Type of change

• New feature (non-breaking change which adds functionality)

How has this been tested?

Tests in bn_test.go pass.

How has this been benchmarked?

ECMUL precompile cost goes from 781,437 to 673,659 SCS.

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[yelhousni]

@ivokub just re-pinging you here

[ivokub]

PR looks good. I'll accept it, but maybe I can try implementing the safe scalarmul with option instead to see how it looks. I have actually also thought about adding an option which would allow to define for MSM which inputs may be unsafe (i.e. 0 scalar or 0 point) and then these options would complement each other quite nicely.

[ivokub]

@yelhousni - I implemented using an option and merged the implementations. See how it looks and feels. If seems excessive then I'm good with reverting. On one hand I do not want to overuse using options, but I still like having unified implementation.

Another thing - currently the default is to use unsafe and we use option to use safe version. But I guess it would make more sense to have the defaults reversed -- i.e. without options we use safe formulas and then can optionally toggle to unsafe formulas for performance. I think we may have incoming bug reports due to the defaults being the other way.
But I didn't want to change now as it would have required a lot of refactoring all over, so dunno.