Patch Notes: No more running in place, lighter shadows and chat roster

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Other players no longer run in place. When a player's movement stops reaching you - they tabbed out, their
connection hiccupped, or the server was restarting - their character used to keep running on the spot (for up to 80
seconds if they never came back). Now they stand still until they move again. That includes players who had already
gone quiet before you arrived in their area.
Distant players in a big crowd walk smoothly. A far-away player whose computer was running at a low frame rate used
to stop and start every second or so; now they keep walking.

Lantern shadows cost much less to prepare. With Steady shadows on (the default), every lantern near a walker or a
swaying tree redraws its shadow every frame, and each of its six shadow views used to look over everything in the
town to find what to draw. Now each lantern looks once, at what can actually reach it - and a still scene does not
look at all. The shadows themselves are exactly what they were.
The chat's player list no longer rebuilds and re-sorts itself every frame while the chat is open. On a busy server
that was costing the frame more the more players were online. The friends list sorts faster too.
Settings are read a little faster everywhere.

PERF-NEXT + RUN-IN-PLACE + AUDIT 637: no more running in place, lighter shadows and chat roster by @Lattymoy in #637

Full Changelog: app-v0.1.6527...app-v0.1.6540