use e2 instances in GCE creation scripts

tools/gce/create_linux_kokoro_performance_worker.sh

@@ -30,7 +30,7 @@ CLOUD_PROJECT=grpc-testing
 ZONE=us-central1-b  # this zone allows 32core machines
 
 INSTANCE_NAME="${1:-grpc-kokoro-performance-server1}"
-MACHINE_TYPE=n1-standard-32
+MACHINE_TYPE=e2-standard-32
 
 gcloud compute instances create "$INSTANCE_NAME" \
     --project="$CLOUD_PROJECT" \

tools/gce/create_linux_kokoro_performance_worker_from_image.sh

@@ -25,7 +25,7 @@ ZONE=us-central1-b  # this zone allows 32core machines
 LATEST_PERF_WORKER_IMAGE=grpc-performance-kokoro-v5  # update if newer image exists
 
 INSTANCE_NAME="${1:-grpc-kokoro-performance-server}"
-MACHINE_TYPE="${2:-n1-standard-32}"
+MACHINE_TYPE="${2:-e2-standard-32}"
 
 gcloud compute instances create "$INSTANCE_NAME" \
     --project="$CLOUD_PROJECT" \

tools/gce/create_windows_debug_worker.sh

@@ -31,7 +31,7 @@ else
   INSTANCE_NAME="${USER}-windows-kokoro-debug1"
 fi
 
-MACHINE_TYPE=n1-standard-8
+MACHINE_TYPE=e2-standard-8
 TMP_DISK_NAME="$INSTANCE_NAME-temp-disk"
 
 gcloud compute disks create "$TMP_DISK_NAME" \