Expose vulkan layer registration in renderdoccmd on win32. Closes #1690

* This is needed so that the functional tests can elevate and run renderdoccmd
  to register the vulkan layer, if needed.
* At the same time remove the old spammy message and ignore flag - this dates
  back to before the UI existed, and that should be the way users run RenderDoc
  generally and it has a good UI for walking through layer registration if
  needed.
* The command is always available, but will only show up in help if attention is
  needed.
* Also fix registering installs on shared drives.

qrenderdoc/Windows/Dialogs/CaptureDialog.cpp

@@ -515,9 +515,11 @@ void CaptureDialog::vulkanLayerWarn_mouseClick()
 
         QStringList renderdoccmdParams;
 
-        renderdoccmdParams << lit("vulkanregister");
+        renderdoccmdParams << lit("vulkanlayer");
         if(system)
           renderdoccmdParams << lit("--system");
+        else
+          renderdoccmdParams << lit("--user");
 
         if(!RunProcessAsAdmin(cmd, renderdoccmdParams, this, true, regComplete))
           regComplete();