tidb-in-kubernetes: migrate tidb operator setup guide (#1503)
tidb-in-kubernetes: migrate tidb operator setup guide (#1503)

* tidb-in-kubernetes: migrate tidb operator setup guide to docs-cn repo

* tidb-in-kubernetes: update wording and format

* tidb-in-kubernetes: update wording

* Update tidb-operator-setup.md

pingcap/docs-cn,pingcap/docs-cn