test: Add comprehensive test coverage for AzureOpenAiChatOptions and PostgresMlEmbeddingOptions

[alxkm]

Adds thorough test coverage for PostgresMlEmbeddingOptions and AzureOpenAiChatOptions which include:

PostgresMlEmbeddingOptions

• Empty and complex kwargs handling
• All vector types and metadata modes validation
• Option merging with null inputs and preservation of original options
• Builder pattern chaining behavior
• Edge cases for complex nested kwargs structures

AzureOpenAiChatOptions

• Minimal configuration options validation
• Empty collections handling (stop lists, logit bias)
• Disabled logprobs configuration
• Single stop sequence processing
• Builder pattern validation
• Parameterized testing for response format types

These tests ensure robust validation of embedding configuration options and proper handling of various input scenarios.
Improves reliability by testing boundary conditions and various configuration scenarios that weren't previously covered.