…e Interfaces (#7081)

* Add a test to verify the messages referencing core are scanned

* Failing test for messages that reference message interfaces

* Unify in one test due avoid assembly loading issues

* Cleanup

* AssemblyScanner should scan assemblies that reference the message interfaces assembly to make sure messages using those interfaces can be discovered and do not act like unobtrusive messages

* Extract into method with a huge comment and inline hints

* Add a type forwarding test as a safety net

* Update src/NServiceBus.Core.Tests/AssemblyScanner/When_using_type_forwarding.cs

Co-authored-by: Phil Bastian <155411597+PhilBastian@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Brandon Ording <bording@gmail.com>

* string.Equals

Co-authored-by: Brandon Ording <bording@gmail.com>

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Co-authored-by: danielmarbach <danielmarbach@users.noreply.github.com>
Co-authored-by: Phil Bastian <155411597+PhilBastian@users.noreply.github.com>
Co-authored-by: Brandon Ording <bording@gmail.com>
(cherry picked from commit 3a7c74c)