Add command line flags to customize diagnostic output of qmlsc/qmlcachegen

qmlsc spits out a lot of warnings about things it cannot compile to C++, and qmlcachegen is completely silent by default. People have been complaining about both. There is the qt.qml.compiler.aot logging category to customize this. However, setting the logging category is inconvenient, especially at build time. Furthermore, people may want a compilation summary that tells them which bindings and functions have been compiled and which have been skipped. Such a summary could be printed to a file specified via a compile option.