Add ingress controller dashboards

[ChrsMark]

What does this PR do?

This PR adds 2 Dashboards based ingress nginx controller fileset (implemented with #16197).

Most of the fields of ingress_controller are the same with access fileset of nginx module. In this most of the visualisations of these new dashboards are just copied from pre existing ones and modified accordingly while others are re-used. There are also some completely new ones. More spcifically:

1. Operating systems breakdown [Filebeat Nginx] ECS, Browsers breakdown [Filebeat Nginx] ECS, Access Map [Filebeat Nginx] ECS. -> reused
2. Top Upstreams [Filebeat Nginx Ingress Controller], Upstream Time Consumed By Path [Filebeat Nginx Ingress Controller], Request Volume By Path [Filebeat Nginx Ingress Controller] -> completely new inspired by some of https://github.com/kubernetes/ingress-nginx/tree/master/deploy/grafana/dashboards#2-request-handling-performance
3. all others are duplicates with modified fileset.name

Why is it important?

To provide out of the box Dashboards for ingress controller service monitoring.

How to test this PR locally

1. Setup ingress controller on minikube following https://kubernetes.io/docs/tasks/access-application-cluster/ingress-minikube/
2. Redirect pods' logs to a temporary file: kubectl -n kube-system logs -f nginx-ingress-controller-6fc5bcc8c9-zm8zv >> /tmp/ingresspod

- module: nginx
  # Ingress-nginx controller logs. This is disabled by default. It could be used in Kubernetes environments to parse ingress-nginx logs
  ingress_controller:
    enabled: true

    # Set custom paths for the log files. If left empty,
    # Filebeat will choose the paths depending on your OS.
    var.paths: ["/tmp/ingresspod"]

4. Setup pipelines and dahsboards in ES
5. Start Filebeat
6. Produce traffic:

1. visit `http://hello-world.info/v2` and `http://hello-world.info` from different browser engines
2. use curl and wget to access the pages with different http words ie: curl -d "param1=value1&param2=value2" -X GET hello-world.info 

Related issues

• Relates [Filebeat] Nginx ingress-controller Dashboard #20897

Screenshots

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #21052 updated]

• Start Time: 2020-09-10T10:59:38.291+0000

• Duration: 50 min 21 sec

Test stats 🧪

Test	Results
Failed	0
Passed	5583
Skipped	825
Total	6408

[sorantis]

Looks great!