review profile, reduce cpu usage

[mmp]

If you launch e.g. the Socal Combined scenario and let it run for a while (so, tons of aircraft), CPU usage is around 100% on my system here. Looking at a profile, there are a bunch of culprits in the STARS code that shouldn't be so dominant:

• 30% of the time is in processEvents() -> MVA Inside(), PointInPolygon()
• 40% of the time is in drawTracks() -> drawRadarTrack() -> drawTrack()
  • 10% is in GLFWPlatform DPIScale() (presumably being called once per aircraft)
  • 10% in MapSlice() to convert the vertices from Point2LL to [2]float32
• 15% is in formatDatablocks(), much of that in datablockType() -> getWarnings()

Part of the datablock-related cost is that both drawLeaderLines() and drawDatablocks() ends up calling formatDatablocks(). Perhaps datablocks should just be cached in STARSAircraftState and only updated when we get a new track.

[mmp]

Starting point from http://localhost:6502/debug/pprof/profile?seconds=30; duration 30s, 25s of samples

• STARSPane Draw 17.6s
  • drawLeaderLines 1.91s
  • drawTracks 6.67s
  • drawDatablocks 1.60s
  • processEvents (-> MVA) 6.36s

[mmp]

This so far brings us down to 5.73s in and under STARSPane Draw, or a 3.07x speedup overall. Probably good enough for now, though when the datablock formatting code gets its next rewrite, we should probably just cache the datablock text.