test: tests for KnowledgeGraphApiLoadProperties::execute()

[gesinn-it-gea]

Goal

includes/api/KnowledgeGraphApiLoadProperties.php:31-63 — execute() is completely untested; only getExamplesMessages() is covered.

Test scenarios

• inversePropsIncluded=true additionally generates -property entries for each given property.
• inversePropsIncluded=false/unset: no inverse entries.
• Multiple nodes (|-separated in the nodes parameter) are processed individually.
• Unknown/invalid titles are skipped.
• Titles already present in self::$data are not processed again.
• Interaction with KnowledgeGraph::setSemanticDataFromApi() with the correct parameters.
• The result is correctly returned as JSON via $result->addValue().

Mocking pattern

• The simplest of the three API classes (no direct SMW store dependency in execute()), so a good entry point.
• setSemanticDataFromApi() may need to be mocked/isolated, or tested with real fixture titles (see the "tests for the main path of setSemanticDataFromApi" issue).

Part of the "raise PHP coverage to ~70%" effort.