v1.20251220.0

What's Changed

• Allow sending Fetcher (service bindings) over RPC by @kentonv in https://github.com/cloudflare/workerd/pull/5693
• move Isolate to it's own struct by @anonrig in https://github.com/cloudflare/workerd/pull/5717
• BodyBufferInputStream migration.. take 3 by @jasnell in https://github.com/cloudflare/workerd/pull/5731
• EW-9753 Enable deprecation warnings for attaching to refcounted objects by @fhanau in https://github.com/cloudflare/workerd/pull/5513

Full Changelog: https://github.com/cloudflare/workerd/compare/v1.20251219.0...v1.20251220.0