Fix example python scripts to work in the UI as well

* In the UI program we can't import renderdoc (it's already imported) so we just
  alias it to rd.

docs/python_api/examples/renderdoc/fetch_counters.py

@@ -1,4 +1,11 @@
-import renderdoc as rd
+import sys
+
+# Import renderdoc if not already imported (e.g. in the UI)
+if 'renderdoc' not in sys.modules and '_renderdoc' not in sys.modules:
+	import renderdoc
+
+# Alias renderdoc for legibility
+rd = renderdoc
 
 draws = {}