Make KingSubsite part of ServConf, handle 404 case more gracefully, make
slog endpoint send SSE headers immediately.
Remaining work mostly revolves around the slog endpoint's slog queue. It
builds up even if nobody is listening, and only the first to pull from
the queue gets to handle/emit the slog event.
There was a TODO in runShips about how the different layers of the
RIO environment had to be changed, so that there was a layer between
KingEnv and PierEnv for things shared between individual Piers, but
which weren't used outside of any PierEnv. This addresses those
TODOs by creating RunningEnv, which for now just owns MultiEyreApi
and makes it so we don't have to pass the entire thing around
explicitly.
The IP handling stuff will go in RunningEnv in a following patch.
