Multithreaded rendering about dawdreamer

[DBraun]

I've started a branch for this here https://github.com/DBraun/DawDreamer/tree/multithread-001

So far it adds a tests/test_multithread.py and sets up the Visual Studio Project to debug the python code. You can put breakpoints in the C++ code too.

1. Build on the command line in an x64 Native Tools for Visual Studio 2022 prompt: msbuild Builds/VisualStudio2022/DawDreamer.sln /property:Configuration=Debug
2. Then make PythonApplication1 the startup project:
3. Then customize the path to the tests/test_multithread.py
4. Then press F5 to launch the debugger

So far I haven't gotten it to work with various attempts:

• py::call_guard<py::gil_scoped_release>() with render in source.cpp
• Having RenderEngine inherit juce::Thread
• Having RenderEngine inherit juce::AudioAppComponent
• Having a new class that inherits AudioAppComponent and having RenderEngine create and destroy it on each render
• Various hacky things with juce::MessageManager::getInstance()->setCurrentThreadAsMessageThread()