wsl2: cleanup commands run with canceled context; errors silently swallowed

## Summary

Follow-up from the review discussion on #4892. The state-change goroutine in `pkg/driver/wsl2/vm_windows.go` has three related robustness issues that remain after the hot-loop fix was merged.

## Issues

### 1. Cleanup runs with a canceled context

Both `stopVM` (`vm_windows.go:59`) and `getWslStatus` (`vm_windows.go:208`) pass `ctx` into `executil.RunUTF16leCommand` via `WithContext(ctx)`. By the time the `<-ctx.Done()` arm runs, that context is already canceled, so the `wsl.exe --list --verbose` and `wsl.exe --terminate` invocations will likely fail immediately with `context canceled`.

The cleanup we kept the goroutine alive for may not actually execute. Using `context.WithoutCancel(ctx)` (or `context.Background()` with a fresh timeout) for the cleanup commands would be more robust.

### 2. `getWslStatus` errors are silently swallowed

The condition `err == nil && status == StatusRunning` means any error (including a `context canceled` error from issue 1) causes the terminate path to be skipped entirely. At minimum, a `logrus.Warnf` on the error would aid debugging.

### 3. `_ = stopVM(...)` discards the terminate error without logging

The return value of `stopVM` is discarded with `_` and no log message is produced if the terminate fails. Adding a `logrus.WithError(err).Warn(...)` would match the logging style used elsewhere in the codebase.

## Suggested fix

- Use `context.WithoutCancel(ctx)` or `context.Background()` with a timeout for cleanup commands in the `<-ctx.Done()` path
- Log `getWslStatus` errors at warn level instead of silently skipping
- Log `stopVM` errors at warn level instead of discarding

cc @jandubois (per review feedback on #4892)