Restore test types for proxy providers

[GuusLieben]

In #934 we restructed a large part of the testing harness for various modules. As a result, several types used for testing got moved around. One incompatibility arose in the ApplicationContextTests for proxy providers. This should be followed up, so the tests can be restored.

Hartshorn/hartshorn-core/src/test/java/test/org/dockbox/hartshorn/ApplicationContextTests.java

Line 110 in 5951773

// TODO: Restore, types were moved to test fixtures, so need new test components