SPIKE: Investigate methods to verify IR generation

For https://codereview.qt-project.org/c/qt/qtdeclarative/+/361700, it would have been nice if we had a way to directly analyse the IR code, and to verify that we generate it correctly.

This might also become useful for further work on the compilers (if we ever optimize the IR code there, or if we want to verify that some QML file only results in IR code that the compiler understands).