Add documentation for new snapshot restore flags

[dusk125]

What would you like to be added?

In #16029, new flags were added to etcdutl snapshot restore (--bump-revision and --mark-compacted) that need user documentation; this issue will add this documentation.

Why is this needed?

The flags are a part of the effort (#16028) to enhance restore without breaking api guarantees, and should be documented so users can understand how they work and what effects they have on their restored etcd instance.

[dusk125]

I can handle this issue

[jmhbnz]

Hey @dusk125 - How are you going with this issue? Please let us know if we should open this issue up for the community, thanks! 🙏🏻

[dusk125]

Hey @jmhbnz, this issue is still on my todo list, but feel free to open it up if someone can/wants to handle it before I get back to this. I've been working on a time sensitive project which is why this and my other PR have stalled, but that is wrapping up, so I'll be able to dedicate more time to both.

[jmhbnz]

Adding contribfest label. This would be a good candidate for the upcoming etcd contribfest at Kubecon.

For a quick hint to whoever picks this up, the flag documentation needs to be added to https://github.com/etcd-io/etcd/blob/main/etcdutl/README.md.

[spawulski]

contribfest: I can try take on this issue

[jmhbnz]

Closing, completed in #16885 :)