Moving Wolfi to usr-merge and sbin-merge

[xnox]

Majority of glibc based distributions use usr-merged file system layout. Some are also moving sbin merged systems. For wolfi to remain a drop-in replacement for these, it is best for Wolfi to adopt these too.

References:

• https://systemd.io/THE_CASE_FOR_THE_USR_MERGE/
• https://fedoraproject.org/wiki/Changes/Unify_bin_and_sbin
• https://discussion.fedoraproject.org/t/f40-change-proposal-unify-usr-bin-and-usr-sbin-system-wide/99853/29

Alpine is working on such a move, but it currently will likely co-incide with upgrade to apk-tools v3:

• https://gitlab.alpinelinux.org/alpine/apk-tools/-/merge_requests/203
• https://gitlab.alpinelinux.org/alpine/tsc/-/issues/89

It generally should be safe to perform usr-merge in stages:

• Move /sbin binaires to /usr/bin and complete /sbin usr-merge
• Move /bin binaries to /usr/bin and complete /bin usr-merge
• Move /lib to usr/lib and complete /lib usr-merge

These are ordered from lowest/largest impact and risk. And possibly we don't do the last one per-se, or do it with smallest number of moves remaining.