Removes `testenv` annotations and related code. These annotations originally let you skip x-pack snippet tests in the docs. However, that's no longer possible.
Relates to #79309, #31619
Adds formal API docs for the following APIs:
* Clear SQL cursor
* SQL search
* SQL translate
Other changes:
* Removes and redirects the "Supported REST parameters section." This is now covered in the SQL search API docs.
* Updates a few related xrefs.
Closes#75085
Adds formal API docs and JSON specs for the following APIs:
* Get async SQL search
* Get async SQL search status
* Delete async SQL search
Closes#74845
