Function launcher

Creates and starts a Fastify HTTP server with the given configuration.

Steps performed:

1. Creates a FastifyInstance merging defaultFastifyOptions with opts.
2. Decorates the instance with locals, verifyToken, and any extra decorators.
3. Registers all plugins and routes.
4. Sets a notFound handler (throws Boom 404) and defaultErrorHandler.
5. Registers preHandler and onResponse hooks.
6. Calls fastify.listen() and invokes the optional done callback.