Merge branch 'en/ort-harden-against-corrupt-trees'

The 'ort' merge backend has been hardened against corrupt trees by ensuring it aborts under appropriate error conditions. * en/ort-harden-against-corrupt-trees: cache-tree: fix verify_cache() to catch non-adjacent D/F conflicts merge-ort: abort merge when trees have duplicate entries merge-ort: free diff pairs queue in clear_or_reinit_internal_opts() merge-ort: drop unnecessary show_all_errors from collect_merge_info() merge-ort: propagate callback errors from traverse_trees_wrapper()