perf(gui): Rebuild static text only when its hotkey setting changes

[tintinhamans]

The static text gadget calls setUseHotkey on every draw, and that always marked the text as changed. So every static text on screen rebuilt its sentence every frame, creating a new D3D surface and texture each time.

setUseHotkey now returns early when the setting and colour are unchanged. That per-frame rebuild was also hiding two other things, which are fixed here too. Render2DSentenceClass::Reset() cleared the hotkey parse setting, so it now leaves it alone and draw() asks the hotkey renderer whether it has a sentence. And a clip region change did not redo the quads, so setClipRegion now marks them for a redo.

This also removes MonoSpaced from Render2DSentenceClass, which was never read.

This is the merged upstream TheSuperHackers#3443 (issue TheSuperHackers#3441), cherry-picked as is. W3DDisplayString exists once per game in this tree, so it is applied to both the GeneralsMD and Generals copies.

Measured on the upstream build in a Zero Hour skirmish at 120 fps, winRepaint went from about 0.155 ms to 0.099 ms per frame, roughly a third less. Hotkey labels, turning the hotkey on and off, text changes and clip changes were checked on screen on the upstream build. Zero Hour builds here; the Generals half could not be compiled in this tree.

This branch was rebuilt on the merged upstream commit. The code is identical to the earlier version of this PR; the two commits are now the one upstream commit.