acceptance: deflake test_demo_node_cmds

[AlexTalks]

Previously the acceptance test test_demo_node_cmds, which attempts to shutdown and decommission some nodes using the cockroach demo CLI, would sometimes be flaky due to delays in propagating information via gossip. This change fixes these flakes by utilizing the virtual table crdb_internal.kv_node_liveness rather than the gossip-based gossip_liveness virtual table.

Fixes: #76391

Release note: None

[cockroach-teamcity]

This change is 

[andrewbaptist]

@AlexTalks Just noticed this - any reason not to merge it?

[AlexTalks]

@AlexTalks Just noticed this - any reason not to merge it?

Nope - will rebase and do so now!

[AlexTalks]

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

---

error creating merge commit from cc1dd90 to blathers/backport-release-22.1-107140: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.1.x failed. See errors above.

---

error creating merge commit from cc1dd90 to blathers/backport-release-22.2-107140: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.2.x failed. See errors above.

---

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}