test: standard circom tests

[florin5f]

No description provided.

[dkales]

You should probably configure your editor to autoformat using rustfmt, the CI catches this.
(if you use rust-analyzer in vscode just enable format on save in settings)

[dkales]

Some discussion points (probably leave open until @fnieddu is back):

• can we import circom stdlib from upstream (e.g., as a submodule) instead of shipping it here
• make generic enough to also easily work with MPC assignment

[dkales]

Another thing to look into: should these all be run on every testrun/ci?
If we want this then we probably have to compile them with optimizations.
Or should we have some external integration test binary that does all this and is only run on demand?