perf: fast path operations for small non-native values

[ivokub]

Description

This PR enforces small non-native values to work on zero or one limb. I also added some fast-path operations when we can deduce the result without needing to perform any operations (mul by zero for example).

Also adds a few more emulation parameters useful for implementing small-fields.

Type of change

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

How has this been tested?

Existing tests succeed

How has this been benchmarked?

Updated the stats.

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

[gbotrel]

lgtm. Shouldn't we also have fast path for Div / Inv / Sqrt ?

[ivokub]

lgtm. Shouldn't we also have fast path for Div / Inv / Sqrt ?

We should. I'll see how we could be able to implement them.

[ivokub]

lgtm. Shouldn't we also have fast path for Div / Inv / Sqrt ?

We should. I'll see how we could be able to implement them.

Added fast paths to Div/Sqrt methods. For inverse we don't support inverse of zero (different from gnark-crypto imo where we take inverse of zero to be zero), so omitted it.

Also added test for checking that the fast paths are complete against short zero (on zero limbs) and large zero.