libstdc++: Define noop coroutine details private and inline [PR 95917]
This moves the __noop_coro_frame type, the __noop_coro_fr global variable, and the __dummy_resume_destroy function from namespace scope, replacing them with private members of the specialization coroutine_handle<noop_coroutine_promise>. The function and variable are also declared inline, so that they generate no code unless used. libstdc++-v3/ChangeLog: PR libstdc++/95917 * include/std/coroutine (__noop_coro_frame): Replace with noop_coroutine_handle::__frame. (__dummy_resume_destroy): Define inline in __frame. (__noop_coro_fr): Replace with noop_coroutine_handle::_S_fr and define as inline. * testsuite/18_support/coroutines/95917.cc: New test. Tested powerpc64le-linux. Committed to trunk.