Move utility functions out of basic.py (#51715)

Move the following methods to lib/anisble/module_utils/common/validation.py:

- _count_terms()
- _check_mutually_exclusive()
- _check_required_one_of()
- _check_required_together()
- _check_required_by()
- _check_required_arguments()
- _check_required_if
- fail_on_missing_params() --> create check_missing_parameters()

test/units/module_utils/common/validation/test_count_terms.py

@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) 2019 Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+import pytest
+
+from ansible.module_utils.common.validation import count_terms
+
+
+@pytest.fixture
+def params():
+    return {
+        'name': 'bob',
+        'dest': '/etc/hosts',
+        'state': 'present',
+        'value': 5,
+    }
+
+
+def test_count_terms(params):
+    check = set(('name', 'dest'))
+    assert count_terms(check, params) == 2
+
+
+def test_count_terms_str_input(params):
+    check = 'name'
+    assert count_terms(check, params) == 1
+
+
+def test_count_terms_tuple_input(params):
+    check = ('name', 'dest')
+    assert count_terms(check, params) == 2
+
+
+def test_count_terms_list_input(params):
+    check = ['name', 'dest']
+    assert count_terms(check, params) == 2