Full temp folders, and steadier overlays

• Fixed: on hosts whose temp folder (/tmp) is full, MC GUI could not build its resource pack ("No space left on device") and pages had no fonts. The pack is now built in memory, and fonts that cannot be copied to the temp folder are kept in plugins/MCGUI/cache/fonts instead.
• Fixed: a player's view zoomed in slightly as an overlay opened and popped back as it closed. It now keeps its width throughout.
• Fixed: overlays sometimes took a second longer to open when another plugin dropped the client's replies. /mcgui debug <player> trace now logs where each open's time goes.
• Overlays now hide see-through text, the world border and particles behind them, including on 1.21.11.
• Fixed: shared compression stopped working for players ViaVersion has nothing to translate for. It works again, so pages open with less CPU on busy servers.