fix(optimizer): settle pending processing promises on close()

[bent0b0x]

Description

createDepsOptimizer().close() cancels the in-flight scan/optimize but does not resolve the current or enqueued depOptimizationProcessing promises. If a dependency is discovered into the current batch while an optimize run is in flight (after that run's startNextDiscoveredBatch() but before it finishes) and the server is then closed, that dep's optimizedDepInfo.processing is left pending forever. Its vite:optimized-deps load() awaits info.processing forever, so the request never leaves environment._pendingRequests and DevEnvironment.close()'s pending-request drain loop never completes — close() never resolves and the process hangs at teardown.

This mirrors runOptimizer()'s pre-optimize closed guard, which already resolves both the current and the enqueued promises; close() just needs to do the same.

Fixes #22934.

Reproduction

Minimal, deterministic repro (Vitest browser mode): https://github.com/bent0b0x/vite-optimizer-orphan-hang — npm test hangs on unpatched vite (reproduced on 8.0.8 and 8.1.4); applying this change makes it exit cleanly.

Note on tests

The failure is a teardown timing race — a dependency discovered mid-optimize plus close() landing while that optimize run is in flight — which is hard to express as a stable unit test without artificial timing hooks. The linked reproduction triggers it deterministically. Happy to add a test in whatever form maintainers prefer.