qmlplugindump needs a way to dump multiple imports into the same file

Previously qmlplugindump silently dumped all imports it considered "related" to the one that was requested. Arguably that behavior was wrong. However, as can be seen in https://codereview.qt-project.org/c/qt/qtquickcontrols/+/275025 and https://codereview.qt-project.org/c/qt/qtdeclarative/+/275004 we want a way to specify something like "qmlplugindump QtQuick.Controls 1.5 QtQuick.Controls.Private 1.5" or "qmlplugindump QtQml 2.14 QML 1.0"