add possibility to set global annotations

[luis-alen]

What motivated this proposal?

so we can globally express additional information related to the chart deployed resources.

What is the proposed change?

add possibility to set global annotations as it's possible with labels with global.labels

Who benefits from this change?

No response

What alternatives have you evaluated?

it's currently possible to add annotations on a per-resource basis, but being able to set it globally is potentially useful.

[mccormickt]

This would be quite valuable even if just exposed for services. For example to control using an Internal LB rather than External for ServiceType: LoadBalancer in GKE:

networking.gke.io/load-balancer-type: "Internal"
https://cloud.google.com/kubernetes-engine/docs/concepts/service-load-balancer