test: Add tests for SpringDocDataRestConfiguration handling of HateoasProperties

[Mattias-Sehlstedt]

Restructures and moves the SpringDocApp39Test which verifies SpringDocDataRestConfiguration when HateoasProperties is not available on the classpath.

This is done since its currently location is amongst the app tests, which does testing entirely differently with a blackbox approach that invokes /v3/api-docs and then verifies the structure of the served payload.

The configuration test folder already has tests that use Spring fixtures for better testing how the classpath is converted to an application context (and offers tools for manipulating it).

This restructure is also tied to #3328 since the best way to illustrate the issue and reason about the best solution is to have SpringDocDataRestConfiguration without HateoasProperties and then showcase that CollectionModelContentConverter, GlobalOpenApiCustomizer and HateoasLinksConverter are now lost since SpringDocHateoasConfiguration has been gated behind HateoasProperties with #3260.