[kibana] add emptyDir volume for kibana data

[ebuildy]

• Chart version not bumped (the versions are all bumped and released at the same time)
• README.md updated with any new values or changes
• Updated template tests in ${CHART}/tests/*.py
• Updated integration tests in ${CHART}/examples/*/test/goss.yaml

Use an emptyDir to store Kibana data instead of Docker overlay, this is a good practice, by setting security context readOnlyRootFilesystem : true .

User can set securityContext via value.yaml file.

(we do that for every Helm releases, elasticsearch/APM/logstash and Kibana, so I can create PR for each if this is a good idea of course).

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[jmlrt]

LGTM⛴

[jmlrt]

jenkins test this please

[ebuildy]

actually, with #1247 PR (extraVolumes), I think we dont need this one any more.

Give a values example should be enough

[botelastic]

This PR has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. To track this PR (even if closed), please open a corresponding issue if one does not already exist.

[botelastic]

This PR has been automatically closed because it has not had recent activity since being marked as stale. Please reopen when work resumes.