[Visualizations] Serverless yml settings (elastic#162959)

## Summary

Adds the necessary yml settings to the serverless config. These settings
are making ui changes in dashboards / visualizations editors and they
apply for all projects.

For testing run `yarn start --serverless=es` and check that the ui is
working as expected with the legacy editors (TSVB, agg based) in a read
only mode.

config/serverless.yml

@@ -77,3 +77,16 @@ console.autocompleteDefinitions.endpointsAvailability: serverless
 
 # Allow authentication via the Elasticsearch JWT realm with the `shared_secret` client authentication type.
 elasticsearch.requestHeadersWhitelist: ["authorization", "es-client-authentication"]
+
+# Visualizations editors readonly settings
+vis_type_gauge.readOnly: true
+vis_type_heatmap.readOnly: true
+vis_type_metric.readOnly: true
+vis_type_pie.readOnly: true
+vis_type_table.readOnly: true
+vis_type_tagcloud.readOnly: true
+vis_type_timelion.readOnly: true
+vis_type_timeseries.readOnly: true
+vis_type_vislib.readOnly: true
+vis_type_xy.readOnly: true
+input_control_vis.readOnly: true