More identifier checks in CoreDocument

[olivereanderson]

Description of change

Currently it is possible to bypass method relationship checks and duplicate verification methods in a document by using Deserialize or the DocumentBuilder. There are also no checks in place to ensure that a service does not share an identifier with a verification method. See #1061. This PR aims to fix these problems.

I have measured the effect on throughput the extra checks introduce and found that they result in about 6-13% longer deserialization times depending on the size of the documents (tested with 495, 1559 and 6112 bytes) . To make it easy for us to try to improve on this in the future and ensure that the numbers don't get worse over time a simple benchmark has been added to the identity_did crate.

Changes to the public API

• In Rust: Many of the setters in CoreDocument and IotaDocument that can lead to broken URI dereferencing have been removed.
• The return type of CoreDocument::remove_method (and IotaDocument::remove_method) has been changed to Option<VerificationMethod> rather than Result<()>. This is to encourage method manipulations going through the checked insert_method API. The same kind of change has also been made to services in documents.
• The legacy crates have been (minimally) adapted to compile with the changes introduced here.
• To accommodate for the new behaviour of remove_* the core data structure OrderedSet has been altered so
  OrderedSet::remove now returns Option<T> instead of bool.

Descoped for this PR

• Ensuring that custom properties do not have overlapping ids with other resources in the document.

Links to any relevant issues

Sub-task of issue #1061.

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

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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