Support for std::thread and std::this_thread

[cfriedt]

Is your enhancement proposal related to a problem? Please describe.
It would be nice for C++ applications to be able to use std::thread and std::this_thread.

Describe the solution you'd like
To be able to use use std::thread and std::this_thread. I can make a PR.

Describe alternatives you've considered
I recently created a PR to provide a sample for and to document the socketpair API (#25528) and was able to get threading working with a couple of defines and implementing std::thread::join().

I also needed nanosleep(2) for std::this_thread::sleep_for()

However, in #25528 it was only partial support for std::thread. There are a couple of additional modes that will need testing. I thought it better to make a separate PR to address C++ threading as a whole.

Additional context

• lib: posix: nanosleep #25559
• Add a Stack Allocation API #26999
• lib: posix: dynamic stack support for pthread_create() #25973
• improve support for c++ threading and synchronization sdk-ng#735

See also

• libgcc: C11 threads-based gthread support cannot link samples/cpp/hello_world out-of-the-box sdk-ng#751