remove github.com/opencontainers/runc dependency

[thaJeztah]

• relates to integrate github.com/opencontainers/runc/libcontainer/user (alternative) moby/sys#134
• relates to RFC: remove user/group name support from libcontainer opencontainers/runc#3998
• relates to Deprecate libcontainer/user, and migrate to github.com/moby/sys/user opencontainers/runc#4017

remove github.com/opencontainers/runc dependency

This migrates uses of github.com/opencontainers/runc/libcontainer/user to the new github.com/moby/sys/user module, which was extracted from runc at commit opencontainers/runc@a3a0ec48c464fe6458d2ba067f6707c027e5384e.

This is the initial release of the module, which is a straight copy, but some changes may be made in the next release (such as fixing camel-casing in some fields and functions (Uid -> UID).

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[AkihiroSuda]

Still draft?

[thaJeztah]

I think it's fine to merge, but also considering if we'd want those nits to be addressed before doing so; any preferences for "this PR" or "follow-up"? opencontainers/runc#4017 (comment)

Thanks! I'll also have a look at fixing the CameCase nits in moby/sys (for a v0.2.0, or whatever version it will be); for this one I wanted it to be a clean "move"

[dmcgowan]

I think it's fine to merge, but also considering if we'd want those nits to be addressed before doing so; any preferences for "this PR" or "follow-up"?

Not a big deal to just get this in as is then if a later version changes the casing, update then.

[thaJeztah]

ok, rebased; let me move it out of draft