Support HarmonyOS (OHOS) in sp_thread_sleep.hpp (missing pthread_setcancelstate)

**Description** When compiling Boost for HarmonyOS (OHOS) using the HarmonyOS SDK/NDK, the compilation fails in boost/core/detail/sp_thread_sleep.hpp because pthread_setcancelstate is not implemented in the HarmonyOS C library (similar to the situation on Android). **Environment** Boost Version: 1.86.0 OS: HarmonyOS Compiler: Clang (HarmonyOS NDK) **Suggested Fix** The file boost/core/detail/sp_thread_sleep.hpp already contains a workaround for __ANDROID__. This should be extended to support __OHOS__ as well. // Proposed change around line 59, 70 and 88 #if defined(BOOST_HAS_THREADS) && !defined(__ANDROID__) && !defined(__OHOS__) This change allows Boost Core to skip the pthread_setcancelstate call on HarmonyOS, ensuring compatibility with its POSIX implementation.