chore: add Kokoro presubmit configs for java-pubsub (#12978)

This is to help test Kokoro jobs in #12963.

Author: meltsufin

.kokoro/presubmit/java-pubsub-graalvm-native-presubmit.cfg

@@ -0,0 +1,42 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+  key: "TRAMPOLINE_IMAGE"
+  value: "gcr.io/cloud-devrel-public-resources/graalvm_sdk_platform_a:3.61.0" # {x-version-update:google-cloud-shared-dependencies:current}
+}
+
+env_vars: {
+  key: "JOB_TYPE"
+  value: "graalvm-single"
+}
+
+# TODO: remove this after we've migrated all tests and scripts
+env_vars: {
+  key: "GCLOUD_PROJECT"
+  value: "gcloud-devel"
+}
+
+env_vars: {
+  key: "GOOGLE_CLOUD_PROJECT"
+  value: "gcloud-devel"
+}
+
+env_vars: {
+  key: "GOOGLE_APPLICATION_CREDENTIALS"
+  value: "secret_manager/java-it-service-account"
+}
+
+env_vars: {
+  key: "SECRET_MANAGER_KEYS"
+  value: "java-it-service-account"
+}
+
+env_vars: {
+  key: "IT_SERVICE_ACCOUNT_EMAIL"
+  value: "it-service-account@gcloud-devel.iam.gserviceaccount.com"
+}
+env_vars: {
+  key: "BUILD_SUBDIR"
+  value: "java-pubsub"
+}

.kokoro/presubmit/java-pubsub-integration.cfg

@@ -0,0 +1,39 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+  key: "TRAMPOLINE_IMAGE"
+  value: "gcr.io/cloud-devrel-kokoro-resources/java8"
+}
+
+env_vars: {
+  key: "JOB_TYPE"
+  value: "integration-single"
+}
+
+# TODO: remove this after we've migrated all tests and scripts
+env_vars: {
+  key: "GCLOUD_PROJECT"
+  value: "gcloud-devel"
+}
+
+env_vars: {
+  key: "GOOGLE_CLOUD_PROJECT"
+  value: "gcloud-devel"
+}
+
+env_vars: {
+  key: "GOOGLE_APPLICATION_CREDENTIALS"
+  value: "secret_manager/java-it-service-account"
+}
+
+env_vars: {
+  key: "SECRET_MANAGER_KEYS"
+  value: "java-it-service-account"
+}
+
+
+env_vars: {
+  key: "BUILD_SUBDIR"
+  value: "java-pubsub"
+}