Remove internal pool management from the WC editor.
The path driver, which wraps this editor, already provides a result pool hierarchy. This can be used by the WC editor instead of having it manage another such hierarchy internally.
Review by: julianfoad
* subversion/libsvn_client/wc_editor.c (edit_baton_t, svn_client__wc_editor_internal): Remove local pool. (dir_baton_t) Remove the local pool users counter. (dir_open_or_add, edit_open, dir_open, dir_add, dir_change_prop, file_open_or_add, file_add): Allocate results in result_pool provided by the caller, i.e. the path driver. (file_close, maybe_done): Remove maybe_done() helper which is now unused.
* subversion/libsvn_client/wc_editor.c (dir_open_or_add): Support opening the root dir. Move higher up. (edit_open): Use dir_open_or_add. (dir_open, dir_add): Adjust callers. (dir_change_prop, file_change_prop): Shorten slightly. (ensure_added_dir): Rename from 'ensure_added', and update callers.