* Replace _suggest endpoint to _search in docs
In 5.0, the _suggest endpoint is just sugar for _search
with suggestions specified. Users should move away from
using the _suggest endpoint, as it is marked as deprecated in 5.x and
will be removed in 6.0
* update docs to use _search endpoint instead of _suggest
* Add deprecation logging to RestSuggestAction
* Use search endpoint instead of suggest endpoint in rest tests