sql/multi-region: warn user with the system db zone config is different than user db

Some customers expect to be able to take out 2 zones and survive. This works when zone survival is configured for their application database. However, the system database do not inherit the application database zone configs and nor should they. But we should at least warn that there is a mismatch. This is useful for cases where customers can configure their app database zone configs but not the system database.

Relates to https://github.com/cockroachdb/cockroach/issues/63365. The ability to make the system DB multiregion is still a preview feature for 24.2, so we should figure out the story for how to productionize it first.

Also see https://github.com/cockroachdb/cockroach/issues/126573. There are rough edges with making the system DB multiregion.

Jira issue: CRDB-39729

Epic CRDB-40070