Add the shareProcessNamespace as a configurable setting in the helm chart

[thomasbruggink]

What this PR does / why we need it:

This PR allows setting the shareProcessNamespace to share processes across containers in the pod.
With this setting enabled its possible for sidecars to signal NGINX to re-open the logs files.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

fixes #8279

How Has This Been Tested?

In a local kubernetes cluster with a container added in extraContainers enabled shareProcessNamespace: true and executed ps in a bash script in the sidecar.

Result with shareProcessNamespace: true:

$ kubectl exec -it --container rotate `kubectl get pods | grep controller | grep Running | cut -d' ' -f1` -- ps ax
PID   USER     TIME  COMMAND
    1 65535     0:00 /pause
    8 www-data  0:00 /usr/bin/dumb-init -- /nginx-ingress-controller --publish-service=default/nginx-ingress-ingress-nginx-controller --election-id=ingress-controller-leader --controller-class=k8s.io/ing
   15 www-data  0:00 /nginx-ingress-controller --publish-service=default/nginx-ingress-ingress-nginx-controller --election-id=ingress-controller-leader --controller-class=k8s.io/ingress-nginx --ingress-c
   23 100       0:00 tini -- /bin/entrypoint.sh fluentd
   29 100       0:01 {fluentd} /usr/bin/ruby /usr/bin/fluentd --config /fluentd/etc/fluent.conf --plugin /fluentd/plugins
   53 root      0:00 /usr/sbin/crond -f -l 0 -L /dev/stdout
   64 100       0:00 /usr/bin/ruby -Eascii-8bit:ascii-8bit /usr/bin/fluentd --config /fluentd/etc/fluent.conf --plugin /fluentd/plugins --under-supervisor
   65 www-data  0:00 nginx: master process /usr/local/nginx/sbin/nginx -c /etc/nginx/nginx.conf
   69 www-data  0:00 nginx: worker process
   70 www-data  0:00 nginx: worker process
   71 www-data  0:00 nginx: worker process
   72 www-data  0:00 nginx: worker process
   73 www-data  0:00 nginx: worker process
  138 www-data  0:00 nginx: worker process
  139 www-data  0:00 nginx: worker process
  140 www-data  0:00 nginx: worker process
  141 www-data  0:00 nginx: cache manager process
  142 www-data  0:00 nginx: cache loader process
  343 root      0:00 bash
  349 root      0:00 ps ax

Result with shareProcessNamespace: false:

$ kubectl exec -it --container rotate `kubectl get pods | grep controller | grep Running | cut -d' ' -f1` -- ps ax
PID   USER     TIME  COMMAND
    1 root      0:00 /usr/sbin/crond -f -l 0 -L /dev/stdout
    7 root      0:00 bash
   13 root      0:00 ps ax

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ thomasbruggink (f9400f9c1c799788c0e5ccde77289a4f35db726d)

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[k8s-ci-robot]

Hi @thomasbruggink. Thanks for your PR.

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[cpanato]

/triage accepted
/kind feature
/priority important-soon

[cpanato]

/approve
/hold for others to comment

thanks for this change

[strongjz]

/lgtm

[strongjz]

/remove-hold
/ok-to-test

[strongjz]

/retest

[strongjz]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, strongjz, thomasbruggink

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