[PATCH 1/3] Make it possible to use several XSL files

The CpptestInputMetric class now extends InputMetricOther. It still uses
an InputMetricXsl instance to do the actual work, but inherits new hooks
that will help detect the tool version automatically.

It still relies on hardcoded values but this is a good starting point.
The dependency to xunit has been bumped to 1.75 in order to get rid of
guice-related issues.

refs JENKINS-18727
[PATCH 2/3] Add a simple version number comparator

refs JENKINS-18727
[PATCH 3/3] Choose the XSL file based on the report version

Starting with cpptest 9.0, the report file format changed slightly,
fortunately the tool version can be found at the same address xml-wise.

This implementation uses a stream reader to avoid completely reading the
report twice: once for the version, and once for the conversion. This is
convenient since the tool version is in the very first element.

refs JENKINS-18727