Add QString overloads for the message/description argument of QVERIFY2 and friends

If the message contains UTF-8 characters (such as the degree symbol of QTBUG-80527) then qtestlib should be able to receive the whole QString, in order to decode it depending on the output. For example:

• console output in the local locale, maybe ISO-8859-1
• XML output in UTF-8

Currently the message string is just a const char * and nobody knows what is its real encoding. I'm talking about macros QVERIFY2(), QSKIP() etc and functions QTestResult::verify() etc.

Eddy vestbo like we discussed today.