Add support for Cloud Run environment variables.

The Java debug agent will now:
Use K_SERVICE to populate the service context (if available).
Use K_REVISION to populate the version context (if available).

PiperOrigin-RevId: 235204086
Change-Id: If683e31c82ac677c22311d9d2f8d4df461eea39b

Author: mctavish

src/agent/internals/src/main/java/com/google/devtools/cdbg/debuglets/java/GcpEnvironment.java

@@ -130,6 +130,9 @@ static Map<String, String> getDebuggeeLabels() {
       if (module == null || module.isEmpty()) {
         module = environmentStore.get("GAE_MODULE_NAME");
       }
+      if (module == null || module.isEmpty()) {
+        module = environmentStore.get("K_SERVICE");
+      }
       if ((module != null) && module.equals("default")) {
         module = null;
       }
@@ -146,6 +149,9 @@ static Map<String, String> getDebuggeeLabels() {
       if (majorVersion == null || majorVersion.isEmpty()) {
         majorVersion = environmentStore.get("GAE_MODULE_VERSION");
       }
+      if (majorVersion == null || majorVersion.isEmpty()) {
+        majorVersion = environmentStore.get("K_REVISION");
+      }
     }
 
     if ((majorVersion != null) && !majorVersion.isEmpty()) {