utest: move cpp from examples to components/libc/cplusplus

Also update the case names to compatible with naming rules.

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>

components/libc/cplusplus/utest/tc_thread.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2006-2019, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2021-09-03     liukang      the first version
+ */
+
+#include <rtthread.h>
+#include "utest.h"
+#include <thread>
+
+static void test_thread(void)
+{
+    int count = 0;
+    auto func = [&]() mutable
+    {
+        for (int i = 0; i < 100; ++i)
+        {
+            ++count;
+        }
+    };
+
+    std::thread t1(func);
+    t1.join();
+
+    if (count != 100)
+    {
+        uassert_false(1);
+    }
+
+    std::thread t2(func);
+    t2.join();
+
+    if (count != 200)
+    {
+        uassert_false(1);
+    }
+
+    uassert_true(1);
+}
+
+static rt_err_t utest_tc_init(void)
+{
+    return RT_EOK;
+}
+
+static rt_err_t utest_tc_cleanup(void)
+{
+    return RT_EOK;
+}
+
+static void testcase(void)
+{
+    UTEST_UNIT_RUN(test_thread);
+}
+UTEST_TC_EXPORT(testcase, "components.libc.cpp.thread_tc", utest_tc_init, utest_tc_cleanup, 10);