Switch isEmpty() to .isPresent() for Optionals Type (#939)

*Issue #, if available:*
Main-build Enablement E2E tests started failing starting from this
[PR](#899).
It was due to the usage of `isEmpty()` for Optional datatypes, which is
available only from Java 11

*Description of changes:*
Change .isEmpty() to .isPresent() for optional types


By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Co-authored-by: Min Xia <xiami@amazon.com>

Author: harrryr

awsagentprovider/src/main/java/software/amazon/opentelemetry/javaagent/providers/AwsMetricAttributeGenerator.java

@@ -502,7 +502,7 @@ private static void setRemoteResourceTypeAndIdentifier(SpanData span, Attributes
       remoteResourceIdentifier = getDbConnection(span);
     }
 
-    if (cloudformationPrimaryIdentifier.isEmpty()) {
+    if (!cloudformationPrimaryIdentifier.isPresent()) {
       cloudformationPrimaryIdentifier = remoteResourceIdentifier;
     }