Refactor public interface to be less strict C and more python friendly

* Generally this means removing ref out parameters and instead returning
  values. In a couple of cases we will want to avoid copies in future
  either by returning const references (e.g. to the pipeline state which
  is immutable).
* At the same time, some pointless bool return values that were always
  true and didn't indicate errors have been removed. They can be added
  again if an error condition comes back.
* Some free functions still have out parameters as C linkage doesn't
  allow returning user types by value.
* The C# UI still invokes into C wrappers for all the C++ classes, which
  handle taking the return value and doing a copy into an out parameter
  still for compatibility.

qrenderdoc/Windows/APIInspector.cpp

@@ -98,8 +98,7 @@ void APIInspector::on_apiEvents_itemSelectionChanged()
   if(ev.callstack.count > 0)
   {
     m_Ctx.Renderer().AsyncInvoke([this, ev](IReplayRenderer *r) {
-      rdctype::array<rdctype::str> trace;
-      r->GetResolve(ev.callstack.elems, ev.callstack.count, &trace);
+      rdctype::array<rdctype::str> trace = r->GetResolve(ev.callstack);
 
       GUIInvoke::call([this, trace]() { addCallstack(trace); });
     });