feat: Add test profile to push metrics to test environment (#1921)

feat:add test profile
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- [ ] Make sure to open an issue as a [bug/issue](https://togithub.com/googleapis/java-bigtable/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)

Fixes 299954521 ☕️

If you write sample code, please follow the [samples format](
https://togithub.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

google-cloud-bigtable-stats/pom.xml

@@ -254,4 +254,12 @@
             </plugin>
         </plugins>
     </build>
+    <profiles>
+        <profile>
+            <id>test</id>
+            <properties>
+                <bigtable.test-monitoring-endpoint/>
+            </properties>
+        </profile>
+    </profiles>
 </project>

google-cloud-bigtable-stats/src/main/java/com/google/cloud/bigtable/stats/BigtableStackdriverStatsExporter.java

@@ -23,6 +23,7 @@
 import com.google.cloud.monitoring.v3.MetricServiceClient;
 import com.google.cloud.monitoring.v3.MetricServiceSettings;
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.MoreObjects;
 import com.google.common.base.Preconditions;
 import io.opencensus.common.Duration;
 import io.opencensus.exporter.metrics.util.IntervalMetricReader;
@@ -44,6 +45,11 @@ public class BigtableStackdriverStatsExporter {
   private static final Duration EXPORT_INTERVAL = Duration.create(60, 0);
   private static final String RESOURCE_TYPE = "bigtable_client_raw";
 
+  private static final String MONITORING_ENDPOINT =
+      MoreObjects.firstNonNull(
+          System.getProperty("bigtable.test-monitoring-endpoint"),
+          MetricServiceSettings.getDefaultEndpoint());
+
   private final IntervalMetricReader intervalMetricReader;
 
   private BigtableStackdriverStatsExporter(
@@ -84,7 +90,7 @@ static MetricServiceClient createMetricServiceClient(Credentials credentials, Du
         MetricServiceSettings.newBuilder()
             .setTransportChannelProvider(InstantiatingGrpcChannelProvider.newBuilder().build());
     settingsBuilder.setCredentialsProvider(FixedCredentialsProvider.create(credentials));
-
+    settingsBuilder.setEndpoint(MONITORING_ENDPOINT);
     org.threeten.bp.Duration timeout = org.threeten.bp.Duration.ofMillis(deadline.toMillis());
     settingsBuilder.createServiceTimeSeriesSettings().setSimpleTimeoutNoRetries(timeout);
     return MetricServiceClient.create(settingsBuilder.build());