WIP: Add custom column printing to openapi spec

[munnerz]

What this PR does / why we need it:

This PR adds custom column printing for ElasticsearchCluster resources. I've not had a chance to test it yet in a live environment.

Special notes for your reviewer:

This builds on #204

Release note:

Print custom columns in output of kubectl get elasticsearchclusters

[jetstack-ci-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: We suggest the following additional approver: munnerz

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[munnerz]

/test e2e v1.8

[munnerz]

/retest

[jetstack-bot]

@munnerz: The following tests failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
navigator-quick-verify	bdef8f1d2fddc7c6990f0fa61f93f10d35958692	link	/test verify
navigator-e2e-v1-9	bdef8f1d2fddc7c6990f0fa61f93f10d35958692	link	/test e2e v1.9
navigator-e2e-v1-7	bdef8f1d2fddc7c6990f0fa61f93f10d35958692	link	/test e2e v1.7
navigator-e2e-v1-8	bdef8f1d2fddc7c6990f0fa61f93f10d35958692	link	/test e2e v1.8

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[jetstack-ci-bot]

@munnerz PR needs rebase