Facilitate filebeat autodiscovery with hints annotation

[pebrc]

When creating Elasticsearch pods we could add a default filebeat annotation

    podTemplate:
      metadata:
        annotations:
          "co.elastic.logs/module": elasticsearch

which would allow filebeat autodiscovery to configure the Elasticsearch filebeat module for the Elasticsearch clusters created by ECK which in turn would give us nicely parsed logs:

and integration with the Stack Monitoring feature in Kibana

I see no harm in the additional annotation for users who don't use filebeat or don't use autodiscovery.

A similar annotation exists for Kibana:

 podTemplate:                                                                                                                                         
    metadata:                                                                                                                                          
      annotations:                                                                                                                                     
        co.elastic.logs/module: kibana