feat(fuzz): Allow index OOB with a small probability

[aakoshh]

Description

Problem*

Follow up for #9786

Summary*

With a 1/10 chance leave out the modulo operation that the fuzzer uses to make sure that an arbitrary index will fall into the bounds of an array or slice. This will most certainly result in "Index out of bounds", and the goal is to make sure all backends handle it the same way.

It is only used if avoid_index_out_of_bounds is false, which we randomise in fuzz targets so that half the time we don't fall into trivial errors, but give the circuit a chance to complete.

Additional Context

This triggered a new bug: #9804

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] 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.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 42feaba	Previous: d672757	Ratio
private-kernel-inner	0.017 s	0.013 s	1.31

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Test Suite Duration'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: e6ed0e1	Previous: 2a5315c	Ratio
test_report_zkpassport_noir_rsa_	2 s	1 s	2

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[rkarabut]

I think I would prefer an explicit option to avoid OOB. I don't like it implicitly depending on avoid_overflow and otherwise being random 🤔

[aakoshh]

Thanks for pointing that out @rkarabut , added a new flag and a default_config function to make it easier to control this initialization.