want `omdb db --destructive` command for manually creating an alert

See https://github.com/oxidecomputer/product-assurance/issues/284#issuecomment-4974066769 --- it would be nice to have a way to manually create an alert from omdb for testing purposes. This should be pretty simple to wire up: an omdb db --destructive alert create command would take an alert class and version argument, and a JSON payload, and just blast it into the omicron.public.alert table using DataStore::alert_create. It would then print out the UUID of the created alert so that Paulina's tests can watch for that UUID being delivered.

Having this is not particularly urgent, since (as I mentioned in https://github.com/oxidecomputer/product-assurance/issues/284#issuecomment-4974066769) we already have integration tests in Omicron that exercise most of what this would let us test. But, it could still be helpful to have real end to end testing for it.

Start by reading DataStore::alert_create in nexus/db-queries/src/db/datastore/alert.rs, then locate the omdb db command implementation and its handling of destructive subcommands. Confirm the alert class, version, and JSON payload arguments, and verify that the command prints the created alert UUID for end-to-end tests to observe.