Make all doc fragments, module utils, and plugin utils private (#11896)

* Make all doc fragments private.

* Make all plugin utils private.

* Make all module utils private.

* Reformat.

* Changelog fragment.

* Update configs and ignores.

* Adjust unit test names.

tests/unit/plugins/module_utils/test__deps.py

@@ -0,0 +1,67 @@
+# (c) 2024, Alexei Znamensky <russoz@gmail.com>
+# Copyright (c) 2024 Ansible Project
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from ansible_collections.community.general.plugins.module_utils import _deps as deps
+
+
+@pytest.fixture
+def module():
+    m = MagicMock()
+    m.fail_json.side_effect = RuntimeError
+    return m
+
+
+def test_wrong_name(module):
+    with deps.declare("sys"):
+        import sys  # noqa: F401, pylint: disable=unused-import
+
+    with pytest.raises(KeyError):
+        deps.validate(module, "wrong_name")
+
+
+def test_fail_potatoes(module):
+    with deps.declare("potatoes", reason="Must have potatoes") as potatoes_dep:
+        import potatoes_that_will_never_be_there  # noqa: F401, pylint: disable=unused-import
+
+    with pytest.raises(RuntimeError):
+        deps.validate(module)
+
+    assert potatoes_dep.failed is True
+    assert potatoes_dep.message.startswith("Failed to import the required Python library")
+
+
+def test_sys(module):
+    with deps.declare("sys") as sys_dep:
+        import sys  # noqa: F401, pylint: disable=unused-import
+
+    deps.validate(module)
+
+    assert sys_dep.failed is False
+
+
+def test_multiple(module):
+    with deps.declare("mpotatoes", reason="Must have mpotatoes"):
+        import potatoes_that_will_never_be_there  # noqa: F401, pylint: disable=unused-import
+
+    with deps.declare("msys", reason="Must have msys"):
+        import sys  # noqa: F401, pylint: disable=unused-import
+
+    deps.validate(module, "msys")
+    deps.validate(module, "-mpotatoes")
+
+    with pytest.raises(RuntimeError):
+        deps.validate(module)
+
+    with pytest.raises(RuntimeError):
+        deps.validate(module, "-msys")
+
+    with pytest.raises(RuntimeError):
+        deps.validate(module, "mpotatoes")