Implement C++ <thread>

[kammce]

To biggest issue with C++ thread library for embedded systems is the inability to support stack size. So we need to come up with a way to support stack size selection and still use the current API. C++ is working to add stack_hint and name to threads which will allow whatever workaround we find to be obsolete once it is in and the compilers support it. But until then, we should find a work around.

One idea, create a sort of array of structs that have a function pointer and a stack size. When thread is used it will check the list for a stack size. If none are present then it will use some default stack size. This would be our of band from the thread library. It would be im hal::freertos.

Or maybe some scoped stack hint object that changes a global (or thread local) stack size value that is then applied to the thread when it starts. Like:

{
  stack_size size(1024);
  std::thread my_thread(f); // stack size is 1024
} // Stack size returns to default amount. 

Maybe this is fine? Some investigation is required.