Make bls12_381_plus dependency more flexible again

[wulfraem]

Description of change

We had issues with bls12_381_plus dependency at version 0.8.16, therefore we pinned the version to 0.8.15. With 0.8.17 being released, we can allow this and following (SemVer compatible) versions.

Also fixed the cargo audit error by using a new release of iota-crypto.

A newer version of clippy had some warnings, that were addressed as well. These were mostly indentations in comments, but one test had a feature flag check, that does not seem to have been used in a Cargo.toml and/or a build.rs, removed the check.

Type of change

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• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix
• Chore

How the change has been tested

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Change checklist

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• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes