Add devstack-prometheus job to validate prometheus plugin

It is a basic devstack job which install prometheus services only.
It will help to validate the plugin fast.

Change-Id: I6d136955192eb15cd03ee3f0824cf537d873bc3c
Signed-off-by: Chandan Kumar (raukadah) <chkumar@redhat.com>

.zuul.yaml

@@ -3,6 +3,39 @@
       jobs:
         - openstack-tox-linters
         - watcher-prometheus-integration
+        - devstack-prometheus
     gate:
       jobs:
         - openstack-tox-linters
+        - devstack-prometheus
+
+- job:
+    name: devstack-prometheus-base
+    nodeset: openstack-single-node-noble
+    abstract: true
+    parent: devstack-base
+    description: |
+      A minimal DevStack base job to install and configure prometheus and
+      node exporter service only.
+    required-projects:
+      - opendev.org/openstack/devstack-plugin-prometheus
+      - opendev.org/openstack/requirements
+    vars:
+      devstack_plugins:
+        devstack-plugin-prometheus: https://opendev.org/openstack/devstack-plugin-prometheus
+      devstack_services:
+        prometheus: true
+        node_exporter: true
+      zuul_copy_output:
+        /etc/prometheus/prometheus.yml: logs
+
+- job:
+    name: devstack-prometheus
+    parent: devstack-prometheus-base
+    description: |
+      A Devstack job to install/configure prometheus and node exporter
+      on a single node and exclude cpu metrics
+    vars:
+      devstack_localrc:
+        # Avoid collecting cpu resources.
+        NODE_EXPORTER_COLLECTOR_EXCLUDE: "cpu"