libarchive: Backport "Fix crash on failure to convert WCS/UTF-8 pathname"

Backport libarchive commit `d4cf95cdac` (archive_write: Fix crash on
failure to convert WCS/UTF-8 pathname to MBS, 2026-02-04) and supporting
parent commits from libarchive PR 2856 [1].

[1] https://github.com/libarchive/libarchive/pull/2856

Issue: #26903
5 files changed