inline simple chat engine as a default

packages/create-llama/templates/index.ts

...s/types/simple/express/src/controllers/chat.controller.ts

...ates/types/simple/express/src/controllers/engine/index.ts

...create-llama/templates/types/simple/express/tsconfig.json

...emplates/types/simple/nextjs/app/api/chat/engine/index.ts

...llama/templates/types/simple/nextjs/app/api/chat/route.ts

...ypes/streaming/express/src/controllers/chat.controller.ts

...s/types/streaming/express/src/controllers/engine/index.ts

...ate-llama/templates/types/streaming/express/tsconfig.json

...lates/types/streaming/nextjs/app/api/chat/engine/index.ts

...ma/templates/types/streaming/nextjs/app/api/chat/route.ts