* Disable ZK in large_config
Speeds up the tests from ~6m to ~1m (debug mode). `large_config` is crate-private so I don't think we need to worry about real users forgetting ZK, and I don't think ZK seems important in these tests, though we should probably have ZK enabled for a couple tests.
A couple tests need ZK or they fail; I added a TODO to look later.
This led to a few other changes:
- Fixed a bug where `trim` could truncate the final poly to a non-power-of-two length. This was improbable when ZK is on due to randomization.
- Gave a few methods access to the whole `CircuitConfig` vs `FriConfig` -- sort of necessary for the above fix, and I don't think there's much downside.
- Remove `cap_height` from `FriConfig` -- didn't really need it any more after giving more methods access to `CircuitConfig`, and having a single copy of the param feels cleaner/safer to me.
* PR feedback
This is detecting the case where we multiply something by 1 and add 0. In that case we can just return the thing being multiplied by 1. We were using the wrong constant to detect this.
Reduces the cost of `compute_evaluation` from 8 to 6 gates.
We previously checked for special cases, like arithmetic on constant Targets, in `arithmetic`. We can handle those cases without actually adding an `ArithmeticGate`.
Now that `arithmetic` just calls `arithmetic_extension`, it makes more sense to check for special cases in the latter method, so it applies to both base and extension field arithmetic.
Reduces gate count from 16149 to 15689.
No functional changes here. The biggest change was moving certain files into new directories like `plonk` and `iop` (for things like `Challenger` that could be used in STARKs or other IOPs). I also split a few files, renames, etc, but again nothing functional, so I don't think a careful review is necessary (just a sanity check).
* Have add_gate take a generic type instead of GateRef
There are a couple advantages
- Users writing their own gates won't need to know about the `GateRef` wrapper; it's more of an internal thing now.
- Easier access to gate methods requiring `self` -- for example, `split_le_base` can just call `gate_type.limbs()` now.
* Update comment
* Always insert
* Division related changes
- Simplify `div_unsafe_extension` using virtual targets
- Add methods for inversion and safe division
As a followup I'll switch some calls to safe division.
* Test safe division also
* add_virtual_extension_target
