Use HTTPS for Tenant Pod UI endpoints

[exalate-issue-sync]

Currently Tenant Pods (cockroach mt start-sql) expose cluster UI JSON endpoints over HTTP. We should modify the server to instead expose these endpoints over HTTPS. They should use the node cert for encryption. We can optionally include support for a ui cert like cockroach start uses but that's less pressing as the tenant's will always be accessed via a reverse proxy.

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