ci: only run default list of graalvm tests if too many modules are touched (googleapis#12216)

Fixes googleapis#12215

Author: chingor13

.kokoro/common.sh

@@ -344,20 +344,20 @@ function run_graalvm_tests() {
 function generate_graalvm_presubmit_modules_list() {
   modules_assigned_list=()
   generate_modified_modules_list
-  if [[ ${#modified_module_list[@]} -gt 0 && ${#modified_module_list[@]} -lt 5 ]]; then
+  if [[ ${#modified_module_list[@]} -gt 4 ]]; then
+    # Too many modules modified, run a subset
+    echo "Too many modules modified, running a subset"
+    module_list="java-aiplatform,java-compute"
+  elif [[ ${#modified_module_list[@]} -gt 0 ]]; then
     # If only a few modules have been modified, focus presubmit testing only on them.
     module_list=$(
       IFS=,
       echo "${modified_module_list[*]}"
     )
   else
-    # If no modules have been modified or if too many have been modified, just test the modules
-    # specified in the MAVEN_MODULES env var.
-    if [ -z "${MAVEN_MODULES}" ]; then
-      echo "MAVEN_MODULES not defined in environment."
-      exit 1
-    fi
-    module_list=${MAVEN_MODULES}
+    # no modules modified
+    echo "No modules modified"
+    module_list=""
   fi
 }
 

.kokoro/presubmit/graalvm-native-a-presubmit.cfg

@@ -31,8 +31,3 @@ env_vars: {
   key: "SECRET_MANAGER_KEYS"
   value: "cloud-java-ci-it-service-account, java-bigqueryconnection-samples-secrets"
 }
-
-env_vars: {
-  key: "MAVEN_MODULES"
-  value: "java-aiplatform,java-compute"
-}

.kokoro/presubmit/graalvm-native-b-presubmit.cfg

@@ -31,8 +31,3 @@ env_vars: {
   key: "SECRET_MANAGER_KEYS"
   value: "cloud-java-ci-it-service-account, java-bigqueryconnection-samples-secrets"
 }
-
-env_vars: {
-  key: "MAVEN_MODULES"
-  value: "java-aiplatform,java-compute"
-}

.kokoro/presubmit/graalvm-native-c-presubmit.cfg

@@ -31,8 +31,3 @@ env_vars: {
   key: "SECRET_MANAGER_KEYS"
   value: "cloud-java-ci-it-service-account, java-bigqueryconnection-samples-secrets"
 }
-
-env_vars: {
-  key: "MAVEN_MODULES"
-  value: "java-aiplatform,java-compute"
-}