Rename unittest_file item to unittest

- constants.py: TYPE_UNITTEST_FILE → TYPE_UNITTEST, cmd "unittest_file" → "unittest"
- All Python files updated: test_item_unittest.py, test_set.py, test_init.py,
  terminal.py, report_export_txt.py, test_tree_item.py
- All .tum files updated (examples, validation, doc)
- Sphinx doc: unittest_file_test_item.rst → unittest_test_item.rst,
  all references updated

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

doc/manual/sphinx/source/test_items/unittest_test_item.rst

@@ -0,0 +1,81 @@
+**unittest** test item
+============================================================
+
+unittest test item allows the execution of unittest test script which
+is part of python standard libraries.
+
+The tum file prototype is as followed:
+
+.. code-block:: yaml
+    :caption: ``unittest`` test item usage example
+
+    - unittest:
+        name: unitTest test item
+        test_file: unitTestScript.py
+        test_method:
+            - test_1
+            - test_2
+
+Attributes
+------------------
+
+Beside common test items attributes, unittest test item has specific attribute, some of which being mandatory.
+
+* ``test_file``: it is the name (and eventually path) of the unittest file
+  to be processed.
+* ``test_method``: it is an optional unittest test sub-item. If one or more
+  elements are present, the unittest python script file is parsed and only
+  the corresponding methods are included in the test tree. Otherwise, all
+  the test methods are included in the test tree.
+
+Access to global variables entries
+----------------------------------
+
+``unittest`` file tests instances have access to the testium global variables
+by using the :ref:`helper's library<sec_python_helper_library>`.
+
+Report value from unittest
+----------------------------------
+
+Value can be added to the test report from unitTest test at runtime.
+
+.. code-block:: python
+    :caption: example of ``unittest`` test item python function
+
+    from  unittest import (TestCase)
+
+    class DummyTests(TestCase):
+        def test_01_report(self):
+            self.reported_values['key reported']= 'value_reported'
+
+Console use example with unittest item
+-----------------------------------------
+
+Here is an example how to use the console module from python ``unittest``.
+
+.. code-block:: python
+    :caption: example of a *testium* console usage from a ``unittest`` python function
+
+    from  unittest import (TestCase)
+    import console
+
+    class DummyTests(TestCase):
+        @classmethod
+        def setUpClass(cls):
+            cls.consA0= console.TelnetConsole('cons name','192.168.98.123',7001)
+            cls.consA0.open()
+            cls.promptA0 = 'test-computer>'
+
+        def test_01_console(self):
+            self.consA0.write('config')
+            self.assertEqual(self.consA0.read_until(self.promptA0, 10), 0)
+            self.consA0.write('lsusb && echo "Done."\n')
+            status, read_data = self.consA0.read_until('Done.',
+                                                        10, return_data=True)
+            self.assertEqual(status, 0)
+            if read_data.find('ID 04f2:b684 Chicony Electronics Co.')!=-1:
+                index=0
+
+        @classmethod
+        def tearDownClass(cls):
+            cls.consA0.close()