Support v0.4: Pin iota-crypto versions

[olivereanderson]

Description of change

The release of iota-crypto version 0.9.2 introduced a breaking change by bumping their bee-ternary dependency to version 0.6.0 which then breaks compilation of bee-pow: 0.2.0 imported by iota-client (see iotaledger/bee#1360 for a better description).

This PR pins dependencies on iota-crypto (and updates the dependency on iota-client) thus making it possible to build identity: ^0.4 without the need for library consumers to adjust their dependencies on iota-crypto (and other breaking crates) in their Cargo.lock file. Note that a fix for the dev branch was merged in #822.

Open questions

• For some reason specifying version ranges >=0.7, <= 0.9.1 for the iota-crypto dependency in identity-iota leads to iota-crypto: 0.9.2 being pulled. It seems like bee-message pulls 0.9.2 instead of using 0.9.1 unless at least one of our crates has a strict equality iota-crypto version =0.9.1. It seems like Cargo is not smart enough to re-use 0.9.1 when given enough freedom. As a somewhat hacky workaround I simply pinned the version to =0.9.1 in identity-iota which did lead to a correct build. Is this OK?
• I could not figure out why the iota-client dependency could not continue using the pinned git hash without breaking builds, but it works now using version ^1.1.1 published on crates.io. Is this OK?

Links to any relevant issues

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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

How the change has been tested

Several builds have been successfully built and tested locally and in the CI.

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

[olivereanderson]

It might be better for iota-crypto to yank the 0.9.2 release. I have asked them whether it would be possible for them to do that here: iotaledger/bee#1360 (comment)