Expose P_DoSpinDashDust to Lua

Part of a series of isolations from !1472 (closed). Exposes P_DoSpinDashDust to Lua. I have used a recreation of this function multiple times over my time modding, so it would be nice to be able to just call it outright. Skip and Whirl use it while running, and Willo and Gemma use it during their fake spindashes.