[stable32] fix(files_external): propagate child copy failures in AmazonS3::copy() - #65006

When copying a directory, copy() discarded the return values of its
recursive calls and always returned true. rename() relies on that value,
so a failed copy still led to rmdir() on the source: every file in the
directory was deleted, the destination stayed empty, and the UI reported
success.

This is reachable whenever a provider rejects CopyObject for objects it
otherwise serves — Hetzner Object Storage answers 501 NotImplemented for
SSE-C encrypted objects, which makes every single child copy fail.

Signed-off-by: Robert Niederreiter <rnix@squarewave.at>