Migrate qtbase to QRegularExpression

The qtbase module is the one needed the more work to be ported to QRegularExpression.

There are several aspects to take into consideration:

• Core tools like moc and qmake can't be ported because pcre can't be built when the bootstrap library is built.
• Classes like QSortFilterProxyModel that now provides QRegularExpression overloads may provide slightly different results between QRegularExpression and QRegExp