Move from std:::thread to Windows Thread Pool

Each frame 8 std::threads are constructed, execute, and are destructed.

Investigate moving to Windows thread pool https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/concurrency-2

Start by locating the per-frame path where eight std::threads are constructed, executed, and destroyed. Read the linked Windows Thread Pool guidance and trace how frame work is coordinated. Done means the thread-pool approach has been evaluated or adopted with equivalent frame behavior and a documented performance or design conclusion.

Written by the indexing model from the issue text.