test: Enhanced test coverage for AzureOpenAiRuntimeHintsTests

[alxkm]

Enhanced test coverage for AzureOpenAiRuntimeHintsTests
Added comprehensive test cases to improve coverage of the AzureOpenAiRuntimeHints class:

• Test infrastructure: Added @BeforeEach setup for better test isolation
• ClassLoader scenarios: Tests with null and custom ClassLoaders
• Member category validation: Ensures all MemberCategory values are registered for Azure model types
• Idempotency testing: Verifies multiple registration calls don't create duplicates for both reflection and resource hints
• Azure-specific validation: Tests for OpenAI client types (sync/async) and model classes registration
• Resource hint verification: Specific tests for /azure-ai-openai.properties resource registration
• Edge case coverage: Empty state validation and package scanning utility method testing

[sobychacko]

Merged via 0ac540d.