chore(rust): move Rust bindings to KZGSettings

[jtraglia]

This moves the public functions to KZGSettings. And we no longer need to pass &kzg_settings as an argument.

Associated with #413.

[asn-d6]

Hmm. I think this is fine, but I have no strong feelings on this PR in either direction.

I will let @mattsse decide if it works better for their codebase.

IIUC this is a non-backwards compatible change and Lighthouse will also need to adjust their codebase.

[mattsse]

this should work but I believe these functions could be kept on Kzgcommitment for backwards compat and then the new fns on kzgsettings would call them?

[jtraglia]

I believe these functions could be kept on Kzgcommitment for backwards compat and then the new fns on kzgsettings would call them?

Hmm that would work too, but it feels a little confusing. I'm okay with breaking backwards compatibility this time. It's a good time to do this, as we're going to make a v2 release soon-ish. I like having all the public functions accessible in the same way.

[mattsse]

changes should be minimal, @Rjected for vis

[Rjected]

This API makes sense to me, fine with updating our code when the new version is released

[asn-d6]

LGTM! Thanks!