Rename internal hooks

After hitting a few "user errors", I think we should rename the following internal hooks for clarity (semvar major, but public api the same)

* `_destroy (cb) --> _close(cb)`
* `_predestroy() -> _destroy(err)`

`_close` to better reflect that its the opposite of `_open` and `_destroy` to indicate that this is the "intercept the statemachine and destroy as soon as you can" hook.

Search the repository for the `_destroy` and `_predestroy` definitions and call sites, then read the related `_open` hook to understand the naming context. Rename the internal hooks consistently while preserving the public API, and verify that no old internal references remain.

Written by the indexing model from the issue text.