Adds tests for Schema 4.5 and modifies existing tests as needed

[codycooperross]

Purpose

This PR adds tests for Schema 4.5 and Schema 4.5 features while adjusting existing tests as-needed.

closes: datacite/datacite#1932

Approach

I copied over the existing 4.4 tests to a spec/kernel-4.5 folder. The tests in spec/kernel-4.5 and spec/kernel-4 are identical, per previous patterns. The XML examples that had been removed in a cleanup were restored to ensure that tests that relied on these files would continue to pass.

Because the kernel-4 XML examples had changed, some tests for earlier versions were changed to target specific schema version examples.

Tests for 4.5 features were added to spec/kernel-4.5/other_spec.rb, spec/kernel-4/other_spec.rb, spec/kernel-4.5/example_relation_type_collects_is_collected_by_spec.rb, and spec/kernel-4/example_relation_type_collects_is_collected_by_spec.rb

Open Questions and Pre-Merge TODOs

Learning

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• New feature (non-breaking change which adds functionality)

• Breaking change (fix or feature that would cause existing functionality to change)

Reviewer, please remember our guidelines:

• Be humble in the language and feedback you give, ask don't tell.
• Consider using positive language as opposed to neutral when offering feedback. This is to avoid the negative bias that can occur with neutral language appearing negative.
• Offer suggestions on how to improve code e.g. simplification or expanding clarity.
• Ensure you give reasons for the changes you are proposing.

[svogt0511]

Looks good.