Add the CRDB HTTP address to DNS, blueprint

[smklein]

This hasn't been strictly necessary in production, because we're re-using the existing CRDB address and just changing the port, but it's necessary for having tests which use "port zero" and receive assignments dynamically.

For a more holistic context, see: nexus/tests/integration_tests/cockroach.rs, where we are now able to access both
the "postgres" and "HTTP" ports via DNS lookup. This will be necessary in subsequent PRs which want to access
this interface to query for Prometheus metrics.

[smklein]

NOTE TO SELF: In ca245f6 , I'm using the "secondary_service_address" part of the blueprint to store the CockroachDB HTTP address.

This seems kinda like it's "Used-as-intended" - if the tests are happy, I really should:

• Add a schema migration that back-fills existing blueprints in the DB, to contain this address with the fixed port
• Perhaps add a data migration test for this use-case

[smklein]

Probably not using this, with preference for #8377