noir_bignum 0.4.0 support

[jp4g]

Description

Problem*

Updates to noir-bignum 0.4.0

Summary*

Updates to use the new noir-bignum api in 0.4.0

Tested to work with 2048 bit keygen so it is 90% of the way done

Additional Context

Todo still:

1. I cannot get the 1024 bit tests working for some reason - gives

error: Failed to solve program: 'Failed to solve brillig function'
  ┌─ /home/user/nargo/github.com/noir-lang/noir-bignumv0.4.0/src/utils/split_bits.nr:86:16
  │
86 │         assert(hi == 0);

2. I have not updated the readme
3. I have not updated the signature gen rust crate to match the new input api

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jp4g]

Also compilation of example on 0.37.0 gives

The application panicked (crashed).
Message:  assertion failed: i < b
Location: /home/runner/work/noir/noir/acvm-repo/acvm/src/compiler/optimizers/merge_expressions.rs:75

from the rsa.verify_sha256_pkcs1v15(hash, bn,65537) line which I have no clue how to address

[iAmMichaelConnor]

Thanks @jp4g, we're working to understand why the 1024-bit test failed. It looks to be a problem with release 0.3.7 of bignum. We'll let you know what we find.

[iAmMichaelConnor]

We've also found the same bug relating to updating to Noir 0.37.0, thanks again! We're investigating that too :)

[TomAFrench]

Thanks for this. We've updated this library to use the new bignum library in #30 so I'm going to close this PR.