Constant mz_catalog::durable::CATALOG_VERSION

pub const CATALOG_VERSION: u64 = 73; // 73u64

The current version of the Catalog. The current version of the Catalog.

We will initialize new Catalogs with this version, and migrate existing Catalogs to this version. Whenever the Catalog changes, e.g. the protobufs we serialize in the Catalog change, we need to bump this version.