* This by no means replaces PySide2, but it allows python extensions to write
simple UIs without needing to rely on PySide2, which might not be available
(generally all windows builds have it as well as recent binary linux builds,
but local windows builds may not and most linux builds probably won't).
* This is a leftover from before the interface was hoisted out, and most
windows were still calling directly to CaptureContext instead of via
the public ICaptureContext interface
* Any work that might use Qt needs to happen on the UI thread, so when
running a python script on the python thread we need to invoke across.
We wrap the main ICaptureContext interface to block invoke onto the UI
for any function calls that aren't just returning internal data.
baldurk