Armory Preview Cache - v23.1

• Frames with no Armory or briefing screen open and nothing loading make two reads of game memory and nothing else, on the ship and in missions: no thread check, clock call, memory check or garbage.
• Measured in game: 0.05 ms per frame on the ship instead of 0.13, and 0.010-0.013 ms in missions instead of 0.035-0.040.
• With rendered thumbnails kept and the Armory closed, memory is checked every 2 seconds instead of every 50 ms, so low memory releases them within 2 seconds.
• Checking the game's asset leases decodes the lease table in place instead of copying it row by row.
• The log adds idle_frames, and verify_gate=1 also turns the idle wait off.