Probe zone creation needs to be in a transaction

[bnaecker]

Converting the TODO from here:

omicron/nexus/db-queries/src/db/datastore/probe.rs

Lines 253 to 263 in 97528cd

	/// Add a probe to the data store.
	pub async fn probe_create(
	&self,
	opctx: &OpContext,
	authz_project: &authz::Project,
	probe: &Probe,
	ip_pool: Option<authz::IpPool>,
	) -> CreateResult<Probe> {
	//TODO in transaction
	use nexus_db_schema::schema::probe::dsl;
	let conn = self.pool_connection_authorized(opctx).await?;

to a proper issue. This creates an external IP address, network interface, and finally the probe itself. These should be in a transaction or otherwise concurrency-safe.

[bnaecker]

This also applies to probe_delete() a few lines below the above.