Change Leader Election Config Map for Chains Controller (#1025)

Currently, the chains controller assumes config-leader-election configmap
as the name for the leader election configmap. This is the default name
for the Knative controllers' leader election configmap. If some other
controllers also exist, it's a good practice to have a separate configmap
for every controller.

config/100-deployment.yaml

@@ -103,6 +103,9 @@ spec:
               value: tekton.dev/chains
             - name: CONFIG_OBSERVABILITY_NAME
               value: tekton-chains-config-observability
+            - name: CONFIG_LEADERELECTION_NAME
+              value: tekton-chains-config-leader-election
+
           ports:
             - name: metrics
               containerPort: 9090

config/config-leader-election.yaml

@@ -0,0 +1,52 @@
+# Copyright 2023 Tekton Authors LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: tekton-chains-config-leader-election
+  namespace: tekton-chains
+  labels:
+    app.kubernetes.io/instance: default
+    app.kubernetes.io/part-of: tekton-chains
+data:
+  _example: |
+    ################################
+    #                              #
+    #    EXAMPLE CONFIGURATION     #
+    #                              #
+    ################################
+    # This block is not actually functional configuration,
+    # but serves to illustrate the available configuration
+    # options and document them in a way that is accessible
+    # to users that `kubectl edit` this config map.
+    #
+    # These sample configuration options may be copied out of
+    # this example block and unindented to be in the data block
+    # to actually change the configuration.
+    # lease-duration is how long non-leaders will wait to try to acquire the
+    # lock; 15 seconds is the value used by core kubernetes controllers.
+    lease-duration: "60s"
+    # renew-deadline is how long a leader will try to renew the lease before
+    # giving up; 10 seconds is the value used by core kubernetes controllers.
+    renew-deadline: "40s"
+    # retry-period is how long the leader election client waits between tries of
+    # actions; 2 seconds is the value used by core kubernetes controllers.
+    retry-period: "10s"
+    # buckets is the number of buckets used to partition key space of each
+    # Reconciler. If this number is M and the replica number of the controller
+    # is N, the N replicas will compete for the M buckets. The owner of a
+    # bucket will take care of the reconciling for the keys partitioned into
+    # that bucket.
+    buckets: "1"