[docker] Set server.shutdownTimeout to match default docker stop timeout

The default setting for `server.shutdownTimeout` is 30s.  Docker's
default stop behavior is to send a SIGKILL after 10s.  This sets the
graceful shutdown behavior to be inline with Docker defaults.

Related to elastic#97223.  Closes elastic#97658

src/dev/build/tasks/os_packages/docker_generator/templates/kibana_yml.template.ts

@@ -18,6 +18,7 @@ function generator({ imageFlavor }: TemplateContext) {
 
   # Default Kibana configuration for docker target
   server.host: "0.0.0.0"
+  server.shutdownTimeout: "10s"
   elasticsearch.hosts: [ "http://elasticsearch:9200" ]
   ${!imageFlavor ? 'monitoring.ui.container.elasticsearch.enabled: true' : ''}
   `);