* add bedrock image gen async support
* added async support for bedrock image gen
* move image gen testing
* add AmazonStability3Config
* add AmazonStability3Config config
* update AmazonStabilityConfig
* update get_optional_params_image_gen
* use 1 helper for _get_request_body
* add transform_response_dict_to_openai_response for stability3
* test sd3-large-v1:0
* unit testing for bedrock image gen
* fix load_vertex_ai_credentials
* fix test_aimage_generation_vertex_ai
* add stability.sd3-large-v1:0 to model cost map
* add stability.stability.sd3-large-v1:0 to docs