* use kubectl consistently throughout for Istio API resource C.R.U.D operations
xref: https://github.com/istio/istio.github.io/issues/1843
* fix typo
* review comments
* remove unnecessary instructions to use `replace` instead of `create`
* fix linter in `zh` content
- Remove What's next sections since we now have auto-generated See also sections
- Fix a few incorrectly capitalized headers, "istio", "kubernetes", "sidecar"