* All tests pass under circom-2 feature flag

- Check for version in WASM, default to version 1
- Include Circom1 when Circom 2 feature flag is enabled

Currently a lot of code duplication. Once Circom-2 is more stable and
proven to work in the wild, feature flag can be removed.

* Separate Circom 1 and Circom2 witness calculation

* Cleanup

* WitnessCalculator helpers for Circom 1 and 2

Also make helper fn private

* Move comment

* Fix expression return

* cargo fmt

* Add cargo test circom-2 to ci