Change API enums to enum class, remove now redundant prefixing

* This gives a little nicer syntax, a bit better type safety, and also
  reflects better for SWIG bindings. Overall it's a minor change but
  better.
* We don't update the C# UI at all, since it's soon to be removed and
  not worth the effort/code churn.
* For now so we're ABI compatible with C#, all enums are uint32_t, but
  that is an obvious optimisation in future to reduce struct packing.
* We avoid 'None' as an enum value, because it's a reserved word in
  python so will cause problems generating bindings.

qrenderdoc/Windows/EventBrowser.cpp

@@ -180,7 +180,7 @@ uint EventBrowser::AddDrawcalls(QTreeWidgetItem *parent, const rdctype::array<Fe
     {
       lastEID = draws[i].eventID;
 
-      if((draws[i].flags & eDraw_SetMarker) && i + 1 < draws.count)
+      if((draws[i].flags & DrawFlags::SetMarker) && i + 1 < draws.count)
         lastEID = draws[i + 1].eventID;
     }
 
@@ -262,7 +262,7 @@ void EventBrowser::on_timeDraws_clicked()
 {
   m_Ctx.Renderer().AsyncInvoke([this](IReplayRenderer *r) {
 
-    uint32_t counters[] = {eCounter_EventGPUDuration};
+    GPUCounter counters[] = {GPUCounter::EventGPUDuration};
 
     rdctype::array<CounterResult> results;
     r->FetchCounters(counters, 1, &results);