Spring-ai refactor(chroma): Align with the latest Chroma API

• Added Jackson annotations for JSON property handling in Chroma API request/response records. Use @JsonInclude(JsonInclude.Include.NON_NULL) to ignore empty fields such as null where. Use @JsonProperty(XYZ) to provide a strong contract with the Cohere API.
• Updated the Docker image for running Chroma locally and in tests to version 0.5.20.
• Enhanced methods with non-null assertions for improved code safety.
• Added a simple search test to verify document similarity search functionality.

Comment From: markpollack

merged in 52999b44b5347e223545b348f42d8a8c99560fa1