The `SwDeviceCreate` completion-callback context (`SwCreateCtx`, the
`sw_create_cb` extern callback, and the `instance_id()` accessor) was
copy-pasted byte-for-byte in the XUSB (`gamepad_windows.rs`) and
DualSense/DS4 (`dualsense_windows.rs`) backends. Hoist the one copy into
`gamepad_raii.rs` as `pub(super)`; both `create_swdevice` bodies now build
the shared type and pass the shared callback. Prunes the now-orphaned
HRESULT/SetEvent/HANDLE imports from the two siblings.
Pure move + dedup, no behavior change. Windows-verified with the rest of
Phase 3 (clippy --all-targets -D warnings).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
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