[Feature] Expose D1 Sessions API (`withSession`) in `worker` / `worker-sys`

### Is there an existing issue for this? - [x] I have searched the existing issues ### Description ## Summary Please expose Cloudflare D1 Sessions API in `worker` and `worker-sys`, so Rust users can use `withSession()` with typed bindings instead of JS reflection interop. ## Current behavior In `worker = 0.7.5` (and `worker-sys = 0.7.5`), D1 currently exposes: - `prepare` - `dump` - `batch` - `exec` But there is no typed API for: - `D1Database.withSession(...)` - `D1DatabaseSession.prepare(...)` - `D1DatabaseSession.batch(...)` - session bookmark methods (if available in runtime API) ## Problem Without typed Sessions support, users must call `withSession` through `js_sys::Reflect` / dynamic JS calls. This has downsides: - no compile-time type safety - more verbose/error-prone code - harder to maintain and review - weaker discoverability for D1 consistency features ## Why it matters For real workloads, Sessions are important for read-after-write consistency and routing behavior (e.g. `first- primary` / bookmark flow). Typed support would make this safe and ergonomic in Rust Workers. ## Proposed API (example) - Add `D1Database::with_session(constraint: Option<&str>) -> Result<D1DatabaseSession>` - Add `D1DatabaseSession::prepare(...)` - Add `D1DatabaseSession::batch(...)` - (Optional) expose bookmark getter/setter if runtime supports it. ## Environment - `worker`: `0.7.5` - `worker-sys`: `0.7.5` - Rust target: `wasm32-unknown-unknown`