Detect context switch callstack samples.

Context switch callstack samples are not included in the sampling data
statistics (as these don't represent random sampling), but are rather put into
a separate dedicated data structure.

For this to work, a complete context switch data has to be available for the
callstack timestamp. There is no guarantee it will be present at the time it
is needed, so a second structure is added to allow postponing qualification of
callstacks.

server/TracyEvent.hpp

@@ -666,9 +666,11 @@ struct ThreadData
     Vector<int64_t> childTimeStack;
     Vector<GhostZone> ghostZones;
     uint64_t ghostIdx;
+    Vector<SampleData> postponedSamples;
 #endif
     Vector<SampleData> samples;
     SampleData pendingSample;
+    Vector<SampleData> ctxSwitchSamples;
     uint64_t kernelSampleCnt;
     uint8_t isFiber;
     ThreadData* fiber;