[vscode] Implement Chat and Language Model initial APIs #13756
Description
VS Code 1.90 introduced the extension support for Chat (ChatParticipant) and Language Models
- see https://code.visualstudio.com/api/extension-guides/language-model
- see https://code.visualstudio.com/api/extension-guides/chat
- see https://github.com/microsoft/vscode/blob/5d6671dacb9d6a582b9354ea317211a8e2b2f918/src/vscode-dts/vscode.d.ts#L19190
- see https://github.com/microsoft/vscode/blob/5d6671dacb9d6a582b9354ea317211a8e2b2f918/src/vscode-dts/vscode.d.ts#L18580