Add more symbols to opentelemetry.util._importlib_metadata (#4181)

Fixes #4180

opentelemetry-api/src/opentelemetry/util/_importlib_metadata.py

@@ -15,15 +15,23 @@
 # FIXME: Use importlib.metadata when support for 3.11 is dropped if the rest of
 # the supported versions at that time have the same API.
 from importlib_metadata import (  # type: ignore
+    Distribution,
     EntryPoint,
     EntryPoints,
+    PackageNotFoundError,
+    distributions,
     entry_points,
+    requires,
     version,
 )
 
-# The importlib-metadata library has introduced breaking changes before to its
-# API, this module is kept just to act as a layer between the
-# importlib-metadata library and our project if in any case it is necessary to
-# do so.
-
-__all__ = ["entry_points", "version", "EntryPoint", "EntryPoints"]
+__all__ = [
+    "entry_points",
+    "version",
+    "EntryPoint",
+    "EntryPoints",
+    "requires",
+    "Distribution",
+    "distributions",
+    "PackageNotFoundError",
+]

opentelemetry-api/tests/util/test__importlib_metadata.py

@@ -19,6 +19,7 @@
 from opentelemetry.util._importlib_metadata import (
     entry_points as importlib_metadata_entry_points,
 )
+from opentelemetry.util._importlib_metadata import version
 
 
 class TestEntryPoints(TestCase):
@@ -106,3 +107,5 @@ def test_uniform_behavior(self):
         entry_points = importlib_metadata_entry_points(group="abc", name="abc")
         self.assertIsInstance(entry_points, EntryPoints)
         self.assertEqual(len(entry_points), 0)
+
+        self.assertIsInstance(version("opentelemetry-api"), str)