Include History and Reference helper elements

[TylerLeonhardt]

Right now the sample has a ton of boilerplate, esp around dealing with history and references:
https://github.com/microsoft/vscode-extension-samples/blob/roblou/tool-user-tsx/chat-tools-sample/src/toolsPrompt.tsx#L151-L279

I blindly copy and pasted this in my chat participant and it works well. I don't really think I need to change anything about it because I would guess that it all "just works" for adding history and references into your prompt.

So if a lot of participants will likely start with this as a base, should we just include in prompt-tsx?