builtin/pack-objects.c: support `--max-pack-size` with `--cruft`
When pack-objects learned the `--cruft` option back in b757353676 (builtin/pack-objects.c: --cruft without expiration, 2022-05-20), we explicitly forbade `--cruft` with `--max-pack-size`. At the time, there was no specific rationale given in the patch for not supporting the `--max-pack-size` option with `--cruft`. (As best I can remember, it's because we were trying to push users towards only ever having a single cruft pack, but I cannot be sure). However, `--max-pack-size` is flexible enough that it already works with `--cruft` and can shard unreachable objects across multiple cruft packs, creating separate ".mtimes" files as appropriate. In fact, the `--max-pack-size` option worked with `--cruft` as far back as b757353676! This is because we overwrite the `written_list`, and pass down the appropriate length, i.e. the number of objects written in each pack shard. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>