Improvements to `renderPrompt`

[TylerLeonhardt]

renderPrompt uses an IChatEndpointInfo:

export interface IChatEndpointInfo {
    /**
     * The maximum number of tokens allowed in the model prompt.
     */
    readonly modelMaxPromptTokens: number;
}

but in VS Code API when we get a model, it looks like this:

    /**
     * Represents a language model for making chat requests.
     *
     * @see {@link lm.selectChatModels}
     */
    export interface LanguageModelChat {

        // ...

        /**
         * The maximum number of tokens that can be sent to the model in a single request.
         */
        readonly maxInputTokens: number;

        // ...
        }

So naturally in several places I have to make this silly object:

{ modelMaxPromptTokens: model.maxInputTokens }

and also pass in model for:

renderPrompt<P extends BasePromptElementProps>(endpoint: IChatEndpointInfo, ctor: PromptElementCtor<P, any>, props: P, model: LanguageModelChat, token: CancellationToken)

so I pass in the same information twice... and I have to massage things to work but we own both APIs.

I think this should be cleaned up to take in only a LanguageModelChat.

This also applies to PromptRenderer.

[connor4312]

@joyceerhl @roblourens I think it makes sense to tweak this to match VS Code's API (such that interfaces are just assignable in most cases) now that it's all finalized. Any reason not to?

[roblourens]

Sounds good

[joyceerhl]

SGTM