* introduce state to the REST API specification
* change state over to stability
* CCR is no GA updated to stable
* SQL is now GA so marked as stable
* Introduce `internal` as state for API's, marks stable in terms of lifetime but unstable in terms of guarantees on its output format since it exposes internal representations
* make setting a wrong stability value, or not setting it at all an error that causes the YAML test suite to fail
* update spec files to be explicit about their stability state
* Document the fact that stability needs to be defined
Otherwise the YAML test runner will fail (with a nice exception message)
* address check style violations
* update rest spec unit tests to include stability
* found one more test spec file not declaring stability, made sure stability appears after documentation everywhere
* cluster.state is stable, mark response in some way to denote its a key value format that can be changed during minors
* mark data frame API's as beta
* remove internal and private as states for an API
* removed the wrong enum values in the Stability Enum in the previous commit
(cherry picked from commit 61c34bbd92f8f7e5f22fa411c6b682b0ebd8a99d)
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