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
The text structure finder API documentation had many references to the "files". While this is one use of the API, the API now has a more generic name. This commit replaces many references to the word "file" to the more generic word "text".
This renames the text structure finder action to match the plugin name.
Also, this adds a new reserved role name so that adding specific permissions for this API is simple.
