chore: remove unused fields for remote model config

[vansangpfiev]

Describe Your Changes

This pull request focuses on simplifying the RemoteModelConfig structure and removing unused fields and methods related to transformation requests and responses. The changes span multiple files, including model_config.h, remote_engine.cc, and remote_engine.h.

Simplification of RemoteModelConfig structure:

• engine/config/model_config.h: Removed unused fields transform_req, transform_resp, metadata, and header_template from RemoteModelConfig. Updated the LoadFromJson, ToJson, and other related methods to reflect these removals. [1] [2] [3] [4] [5] [6] [7]

Removal of transformation request and response handling:

• engine/extensions/remote-engine/remote_engine.cc: Removed handling of transform_req and transform_resp in various methods, including MakeStreamingChatCompletionRequest, MakeChatCompletionRequest, LoadModelConfig, LoadModel, and HandleChatCompletion. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Update to ModelConfig struct:

• engine/extensions/remote-engine/remote_engine.h: Removed api_key, transform_req, and transform_resp fields from the ModelConfig struct.

Fixes Issues

• Closes #
• Closes #

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed