test: Add robust null safety and configuration testing for Azure OpenAI embeddings and Google GenAI runtime hints

[alxkm]

This PR adds comprehensive robustness testing for Azure OpenAI embeddings and Google GenAI runtime hints registration, focusing on null safety, configuration edge cases, and proper hint type isolation.

Changes Made

Azure OpenAI Embedding Tests

Null Safety Validation

• shouldHandleNullInputList - Verifies graceful handling of null input lists
• shouldHandleNullEmbeddingRequest - Ensures proper exception handling for null requests

Configuration Testing

• shouldHandlePartialOptionsOverride - Tests mixing custom options with defaults
• shouldHandleDefaultOptionsOnlyClient - Validates minimal configuration scenarios

Google GenAI Runtime Hints Tests

ClassLoader Robustness

• registerHintsWithNullClassLoader - Ensures hints registration works with null ClassLoader

Hint Type Isolation

• verifyNoProxyHintsAreRegistered - Confirms only reflection hints are registered
• verifyNoSerializationHintsAreRegistered - Validates clean hint scope without serialization hints

Benefits

• Prevents NullPointerException crashes in production environments
• Ensures robust configuration handling with partial option overrides
• Validates proper fallback to default configurations
• Confirms correct hint registration for native compilation
• Prevents hint bloat by validating only necessary hint types are registered
• Ensures ClassLoader independence for flexible deployment scenarios

[ilayaperumalg]

@alxkm Thanks for the PR and @sunyuhan1998 Thanks for the review.