C++: Moved all C++ examples to own folder

* moved C++ examples to a new cxx folder in
  examples
* added experimental C++ component
* added ESPException class to the C++ experimental
  component
* added test cases for ESPException and
  corresponding test macros

examples/cxx/exceptions/example_test.py

@@ -0,0 +1,23 @@
+from __future__ import print_function
+
+import ttfw_idf
+
+
+@ttfw_idf.idf_example_test(env_tag='Example_WIFI')
+def test_examples_system_cpp_exceptions(env, extra_data):
+    dut = env.get_dut('cpp_exceptions_example', 'examples/system/cpp_exceptions', dut_class=ttfw_idf.ESP32DUT)
+    # start test
+    dut.start_app()
+    lines = ['app_main starting',
+             'In constructor, arg=42',
+             'In constructor, arg=0',
+             'In destructor, m_arg=42',
+             'Exception caught: Exception in constructor',
+             'app_main done'
+             ]
+    for line in lines:
+        dut.expect(line, timeout=2)
+
+
+if __name__ == '__main__':
+    test_examples_system_cpp_exceptions()