Update to iota-client 2.0.1-rc.4 and iota-client-wasm 0.5.0-alpha.6

[olivereanderson]

Description of change

For the Rust library:

• Updates iota-client dependency to version 2.0.1-rc.4 which enables building the Rust library without pinning iota-types to a fixed older version.
• The IotaIdentityClient trait has been simplified.
• The IotaIdentityClientExt now contains some additional methods that are implemented in terms of IotaIdentityClient::get_protocol_parameters which were previously standalone methods on IotaIdentityClient.

For the JS bindings:

• Updates the dependency on @iota/iota-client-wasm to 0.5.0-alpha.6 which changes the interface to the client somewhat. In particular one can now obtain a Client using a normal constructor (i.e. async Client.new is no longer necessary).
• Simplifies the IIotaIdentityClient interface.

Type of change

Add an x to the boxes that are relevant to your changes.

• 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

Examples run locally.

Change checklist

Add an x to the boxes that are relevant to your changes.

• 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

[PhilippGackstatter]

Looks good to me, thanks!