Change the staging neon-proxy-scram update strategy to RollingUpdate (#3678)

## Describe your changes
When we deploy the proxy with the default Recreate strategy, there's
always some downtime and existing connections will be shut down. Change
the strategy to RollingUpdate and delay the kill signal by one week. AWS
Network Loadbalancer keeps the existing connections alive for as long as
the pods are alive, but will direct new connections to new pods.


## Issue ticket number and link
https://github.com/neondatabase/neon/issues/3333

.github/helm-values/dev-eu-west-1-zeta.neon-proxy-scram.yaml

@@ -1,6 +1,21 @@
 # Helm chart values for neon-proxy-scram.
 # This is a YAML-formatted file.
 
+deploymentStrategy:
+  type: RollingUpdate
+  rollingUpdate:
+    maxSurge: 100%
+    maxUnavailable: 50%
+
+# Delay the kill signal by 7 days (7 * 24 * 60 * 60)
+# The pod(s) will stay in Terminating, keeps the existing connections
+# but doesn't receive new ones
+containerLifecycle:
+  preStop:
+    exec:
+      command: ["/bin/sh", "-c", "sleep 604800"]
+terminationGracePeriodSeconds: 604800
+
 image:
   repository: neondatabase/neon
 

.github/helm-values/dev-us-east-2-beta.neon-proxy-scram.yaml

@@ -1,6 +1,21 @@
 # Helm chart values for neon-proxy-scram.
 # This is a YAML-formatted file.
 
+deploymentStrategy:
+  type: RollingUpdate
+  rollingUpdate:
+    maxSurge: 100%
+    maxUnavailable: 50%
+
+# Delay the kill signal by 7 days (7 * 24 * 60 * 60)
+# The pod(s) will stay in Terminating, keeps the existing connections
+# but doesn't receive new ones
+containerLifecycle:
+  preStop:
+    exec:
+      command: ["/bin/sh", "-c", "sleep 604800"]
+terminationGracePeriodSeconds: 604800
+
 image:
   repository: neondatabase/neon