Migrate CAPO build and test job to eks cluster

This migrates the CAPO presubmit jobs that does not depend on GCE.
It also adds resource limits (set to the same as the requests) since
this is required in the new cluster.

config/jobs/kubernetes-sigs/cluster-api-provider-openstack/cluster-api-provider-openstack-presubmits.yaml

@@ -1,6 +1,7 @@
 presubmits:
   kubernetes-sigs/cluster-api-provider-openstack:
   - name: pull-cluster-api-provider-openstack-build
+    cluster: eks-prow-build-cluster
     always_run: true
     optional: false
     decorate: true
@@ -19,10 +20,14 @@ presubmits:
           requests:
             memory: "6Gi"
             cpu: "2"
+          limits:
+            memory: "6Gi"
+            cpu: "2"
     annotations:
       testgrid-dashboards: sig-cluster-lifecycle-cluster-api-provider-openstack
       testgrid-tab-name: pr-build
   - name: pull-cluster-api-provider-openstack-test
+    cluster: eks-prow-build-cluster
     always_run: true
     optional: false
     decorate: true
@@ -36,6 +41,9 @@ presubmits:
           requests:
             memory: "6Gi"
             cpu: "2"
+          limits:
+            memory: "6Gi"
+            cpu: "2"
     annotations:
       testgrid-dashboards: sig-cluster-lifecycle-cluster-api-provider-openstack
       testgrid-tab-name: pr-test