fix: Fix remaining issues in Brillig's copy on write arrays

[jfecher]

Description

Problem*

Fixes remaining todo and some panics in #3522

Summary*

I'm not sure if unpacking the entire slice recursively to complete the todo!() is even possible so I tried a different (hopefully sound) approach of incrementing the Rc for sub-arrays on each ArrayGet and when constructing the array. I've also disabled the IncrementRc instruction when not in Brillig code since it is unneeded.

Additional Context

I'm targetting @sirasistant's PR so that it is easier to see the changes I made to it. If all is well, we can merge this PR and then his afterward to get the feature in.

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [Exceptional Case] Documentation to be submitted in a separate PR.

PR Checklist*

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

[jfecher]

Testing this on noir-rsa I get the following panic:

[rsa] Testing test_verify_sha256_pkcs1v15_512... The application panicked (crashed).
Message:  internal error: entered unreachable code: ICE: Expected vector, got BrilligArray(BrilligArray { pointer: RegisterIndex(45), size: 56, rc: RegisterIndex(46) })
Location: compiler/noirc_evaluator/src/brillig/brillig_ir/brillig_variable.rs:74

[jfecher]

Interesting, the compile_success_empty_brillig_integer_binary_operations test is failing but only when running cargo t and not cargo t --release

---- tests::compile_success_empty_brillig_integer_binary_operations stdout ----
thread 'tests::compile_success_empty_brillig_integer_binary_operations' panicked at '`nargo info` failed with: The application panicked (crashed).
Message:  internal error: entered unreachable code: ICE: Expected vector, got BrilligArray(BrilligArray { pointer: RegisterIndex(6), size: 32, rc: RegisterIndex(7) })
Location: compiler/noirc_evaluator/src/brillig/brillig_ir/brillig_variable.rs:74

Edit: This was on linux. On mac it looks like it panics in both debug and release.

[sirasistant]

Looks great to me!