add grafana ldap support

(cherry picked from commit ce7007c568)

jsonnet/kube-prometheus/components/grafana.libsonnet

@@ -27,6 +27,7 @@ local defaults = {
   containers: [],
   datasources: [],
   config: {},
+  ldap: null,
   plugins: [],
   env: [],
 };
@@ -57,6 +58,7 @@ function(params) {
         folderDashboards: g._config.folderDashboards,
         containers: g._config.containers,
         config+: g._config.config,
+        ldap: g._config.ldap,
         plugins+: g._config.plugins,
         env: g._config.env,
       } + (