Use UTF-8 in the QtTest data and benchmark tags

Use UTF-8 in the QtTest data and benchmark tags

Future-proofing. Since Qt source code is now mandated to be in UTF-8,
it is entirely possible that someone will use non-ASCII in data tags.

Though it would be interesting to see how to access them from the
Windows command-line.

Change-Id: I880fc312432b62143888ff1e1d9abbd54f704601
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>