chore: Save witness in correct format that bb.js expects

[vezenovm]

Description

We are moving to have our ACIR tests run in bb.js for proving and verification while nargo will just handle circuit execution.

Problem*

Resolves

Summary*

This PR changes the format in which witnesses are saved to file. bberg is currently the only consumer of our witness output however this may be breaking for any old programs that still save the witness to file and use it elsewhere (however I see this as unlikely due to the large divergence in the TS bberg packages and Noir master).

In order to be in line with bb.js we also need to enable the RecursiveAggregation opcode in acvm-backend-barretenberg as per this PR: noir-lang/acvm-backend-barretenberg#225

Documentation

• This PR requires documentation updates when merged.

  • I will submit a noir-lang/docs PR.
  • I will request for and support Dev Rel's help in documenting this PR.

Additional Context

PR Checklist*

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

[TomAFrench]

This breaks any interop with the ACVM simulator. bb.js should update to accept the witness map format defined by ACIR.

[vezenovm]

This breaks any interop with the ACVM simulator. bb.js should update to accept the witness map format defined by ACIR.

Ah didn't realize this would break ACVM simulator. I switched this to a feature flag

[Savio-Sou]

bb.js should update to accept the witness map format defined by ACIR.

@TomAFrench could you open an issue for it on https://github.com/AztecProtocol/barretenberg/?

This has now been put behind a feature flag

[TomAFrench]

Reminder that we should not merge PRs which rely on patched versions of our own packages. This PR should have used the 0.6.1 release of acvm-backend-barretenberg.

Using a commit which wasn't in master for acvm-backend-barretenberg resulted in nightly releases failing and 0.8.0 failing on some targets.