Repository: conan-io/conan

Issue:
[BUG] Conan Tools does not export detected_os
To help us debug your issue please explain:

When I was updating cmake_installer, I just found that `detected_os` is not exported by conans.tools

Conan Version 1.15.0

```python
from conans import tools

if __name__ == "__main__":
	tools.detected_os()
```

**ERROR**: 
```
Traceback (most recent call last):
  File "conanfile.py", line 4, in <module>
    tools.detected_os()
AttributeError: module 'conans.tools' has no attribute 'detected_os'
```

- [X] I've read the [CONTRIBUTING guide](https://github.com/conan-io/conan/blob/develop/.github/CONTRIBUTING.md).
- [X] I've specified the Conan version, operating system version and any tool that can be relevant.
- [X] I've explained the steps to reproduce the error or the motivation/use case of the question/suggestion.



Discussion:
uilianries: What? migration test error? But my patch is only about an unit test ... Go home Jenkins, you are drunk

https://conan-ci.jfrog.info/blue/organizations/jenkins/ConanTestSuite/detail/PR-5102/1/pipeline#step-131-log-1309
lasote: Merge develop to get rid of that error. 
jgsogo: @uilianries, please merge upstream, it should solve the error in CI. Thanks!
uilianries: @jgsogo done! let's see the result :)

Patch:
diff --git a/conans/tools.py b/conans/tools.py
index ee26518ea..5647ce862 100644
--- a/conans/tools.py
+++ b/conans/tools.py
@@ -111,6 +111,7 @@ def replace_path_in_file(*args, **kwargs):
 # from conans.client.tools.oss
 args_to_string = tools_oss.args_to_string
 detected_architecture = tools_oss.detected_architecture
+detected_os = tools_oss.detected_os
 OSInfo = tools_oss.OSInfo
 cross_building = tools_oss.cross_building
 get_cross_building_settings = tools_oss.get_cross_building_settings


Test patch:
diff --git a/conans/test/unittests/client/conf/detect/detected_os_test.py b/conans/test/unittests/client/conf/detect/detected_os_test.py
index e5a1aac9a..1da5b708a 100644
--- a/conans/test/unittests/client/conf/detect/detected_os_test.py
+++ b/conans/test/unittests/client/conf/detect/detected_os_test.py
@@ -5,6 +5,7 @@
 import unittest
 from mock import mock
 from conans.client.tools.oss import detected_os, OSInfo
+from conans import tools
 
 
 class DetectedOSTest(unittest.TestCase):
@@ -44,3 +45,7 @@ class DetectedOSTest(unittest.TestCase):
     def test_solaris(self):
         with mock.patch("platform.system", mock.MagicMock(return_value='SunOS')):
             self.assertEqual(detected_os(), "SunOS")
+
+    def test_export_tools(self):
+        with mock.patch("platform.system", mock.MagicMock(return_value='FreeBSD')):
+            self.assertEqual(tools.detected_os(), "FreeBSD")