Reuse NewResourceMetadataEnricher to reduce memory utilisation

[ChrsMark]

In the kubernetes module for every metricset enabled we are creating a different MetadataEnricher by calling the NewResourceMetadataEnricher method:

beats/metricbeat/module/kubernetes/util/kubernetes.go

Line 130 in 0405168

func NewResourceMetadataEnricher(

This means that many k8s resources like Nodes, Namespaces are being retrieved multiple times through Watchers.
Same for Pods that are being retrieved from pod, container, state_pod and state_container metricsets.

This has apparently impact on the memory utilization of Metricbeat and can lead in Metricbeat Pod requiring a lot of memory resources to avoid being OOMKilled. We can improve this by establishing a common "pool" of Enrichers by type for the whole module and then each metricset can re-use the proper Enricher accordingly.

This also affects Elastic Agent since it runs Metricbeat under the hood.

cc: @gizas @tommyers-elastic @bturquet

[MichaelKatsoulis]

Duplicate of #37243