Add test for metric uninstrument and add _supports_metrics flag

Author: shalevr

Diff for: instrumentation/README.md

@@ -40,5 +40,5 @@
 | [opentelemetry-instrumentation-system-metrics](./opentelemetry-instrumentation-system-metrics) | psutil >= 5 | No
 | [opentelemetry-instrumentation-tornado](./opentelemetry-instrumentation-tornado) | tornado >= 5.1.1 | No
 | [opentelemetry-instrumentation-urllib](./opentelemetry-instrumentation-urllib) | urllib | No
-| [opentelemetry-instrumentation-urllib3](./opentelemetry-instrumentation-urllib3) | urllib3 >= 1.0.0, < 2.0.0 | No
+| [opentelemetry-instrumentation-urllib3](./opentelemetry-instrumentation-urllib3) | urllib3 >= 1.0.0, < 2.0.0 | Yes
 | [opentelemetry-instrumentation-wsgi](./opentelemetry-instrumentation-wsgi) | wsgi | Yes

Diff for: instrumentation/opentelemetry-instrumentation-urllib3/src/opentelemetry/instrumentation/urllib3/package.py

@@ -14,3 +14,5 @@
 
 
 _instruments = ("urllib3 >= 1.0.0, < 2.0.0",)
+
+_supports_metrics = True

Diff for: instrumentation/opentelemetry-instrumentation-urllib3/tests/test_urllib3_ip_support.py

@@ -103,6 +103,19 @@ def tearDown(self):
         super().tearDown()
         URLLib3Instrumentor().uninstrument()
 
+    def test_metric_uninstrument(self):
+        with urllib3.PoolManager() as pool:
+            pool.request("GET", self.http_url)
+            URLLib3Instrumentor().uninstrument()
+            pool.request("GET", self.http_url)
+
+            metrics_list = self.memory_metrics_reader.get_metrics_data()
+            for resource_metric in metrics_list.resource_metrics:
+                for scope_metric in resource_metric.scope_metrics:
+                    for metric in scope_metric.metrics:
+                        for point in list(metric.data.data_points):
+                            self.assertEqual(point.count, 1)                            
+
     def test_basic_metric_check_client_size_get(self):
         with urllib3.PoolManager() as pool:
             start_time = default_timer()