Doubling down on local development with Workers: Miniflare meets workerd

Introduced Miniflare 3, powered by the open-sourced `workerd` runtime, providing bug-for-bug compatibility with the Cloudflare Workers production environment. This significantly reduces behavior mismatches and simplifies local development. Added experimental opt-in support for accessing real Workers KV namespaces locally. Announced that `wrangler dev --local` will become the default, offering substantial reductions in startup and script reload times. Introduced `wrangler init --from-dash` to easily set up local projects from existing dashboard-developed Workers.