Add integration test for contract artifact output

[TomAFrench]

The PR #1126 resulted in a regression due to insufficient testing on the contract artifacts being saved to disk. This was fixed in #1158 but it was brought up that:

I wonder if we can have PR artifacts that show what the ABI looks like, or possibly some ABI artifact that gets checked in and the CI checks if they match

Originally posted by @kevaundray in #1158 (comment)

We should add an integration test which checks the build artifacts from a set Noir project against some checked in examples in order to avoid this happening in future.

[ameya-deshmukh]

Would love to take this up @TomAFrench!