[modules/cpu3] Add new CPU module

Based on cpu2 module, but use `sensors -j` and some json path walking to
better parse CPU temp and fan speeds. The output of `sensors -u` can
contain many duplicates of the same sensor name, but from different
sensor device paths.

Signed-off-by: SuperQ <superq@gmail.com>

tests/modules/contrib/test_cpu3.py

@@ -0,0 +1,6 @@
+import pytest
+
+pytest.importorskip("psutil")
+
+def test_load_module():
+    __import__("modules.contrib.cpu3")