QEventLoop related issues on the main thread
This class should be used whenever a blocking process run is required.
Unlike implementations which rely on QApplication::processEvents()
or creation of a QEventLoop, this class is completely thread safe
and can be used on either the main thread or background threads without
issue.
Execution supports use of a QgsFeedback object to support termination
of the process.
This is a useful method, and desirable in Qt < 5.15. It's also not
exposed currently to Python, so this doubles as a way for plugins
to use this method.
