Changed logging in DoTimed/RunActivity to create less overhead.

- Refactored PerfTimer to use less memory.
- Avoid using the PerfTimer in highly called methods DoTimed and RunActivity, instead tracking long ticks manually to reduce overhead and avoid memory allocations.
- Added some helper methods in PerfTimer to output information when a tick takes too long.
- Changed PerfTimer logging to output the time at the start of the line, and no longer truncate output per line.
- Settings.LongTickThreshold changed from TimeSpan to float and renamed to LongTickThresholdMs.

OpenRA.Game/Settings.cs

@@ -71,7 +71,7 @@ namespace OpenRA
 		public bool BotDebug = false;
 		public bool PerfText = false;
 		public bool PerfGraph = false;
-		public TimeSpan LongTickThreshold = TimeSpan.FromMilliseconds(1d);
+		public float LongTickThresholdMs = 1;
 		public bool SanityCheckUnsyncedCode = false;
 		public int Samples = 25;
 		public bool IgnoreVersionMismatch = false;